Disorder is a lack of order — in other words, chaos, clutter, and general disarray.

If everyone in your class is yelling and throwing things, there's no order: there's disorder. If all the library books are out of order and thrown sloppily on the shelf, that's disorder, too. If you mess or mix something up, you're disordering it. Many medical conditions and diseases are also called disorders, like post-traumatic stress disorder. Whenever there's disorder, something is wrong or out of whack.

Definitions of disorder
  1. noun
    a condition in which things are not in their expected places
    “the files are in complete disorder
    synonyms: disorderliness
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    order, orderliness
    a condition of regular or proper arrangement
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    a condition of great disorder
    the condition of being untidy
    mess, messiness, muss, mussiness
    a state of confusion and disorderliness
    disarrangement, disorganisation, disorganization
    a condition in which an orderly system has been disrupted
    clutter, fuddle, jumble, mare's nest, muddle, smother, welter
    a confused multitude of things
    sloppiness, slovenliness, unkemptness
    a lack of order and tidiness; not cared for
    a jumble of things to be given away
    type of:
    condition, status
    a state at a particular time
  2. noun
    a physical condition in which there is a disturbance of normal functioning
    “the doctor prescribed some medicine for the disorder
    synonyms: upset
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    immunological disorder
    a disorder of the immune system
    functional disorder
    disorder showing symptoms for which no physiological or anatomical cause can be identified
    organic disorder
    disorder caused by a detectable physiological or structural change in an organ
    the condition in which the upper teeth do not touch the lower teeth when biting
    abruptio placentae
    a disorder of pregnancy in which the placenta prematurely separates from the wall of the uterus
    an abnormal deficiency or absence of free hydrochloric acid in the gastric juice; often associated with severe anemias and cancer of the stomach
    acholia, cholestasis
    a condition in which little or no bile is secreted or the flow of bile into the digestive tract is obstructed
    achylia, achylia gastrica
    absence of gastric juices (partial or complete)
    acute brain disorder, acute organic brain syndrome
    any disorder (as sudden confusion or disorientation) in an otherwise normal person that is due to reversible (temporary) impairment of brain tissues (as by head injuries or drugs or infection)
    ailment, complaint, ill
    an often persistent bodily disorder or disease; a cause for complaining
    eating disorder
    a disorder of the normal eating routine
    bladder disorder
    a disorder of the urinary bladder
    cardiovascular disease
    a disease of the heart or blood vessels
    celiac disease
    a disorder in children and adults; inability to tolerate wheat protein (gluten); symptoms include foul-smelling diarrhea and emaciation; often accompanied by lactose intolerance
    cheilosis, perleche
    a disorder of the lips marked by scaling and fissures at the corners of the mouth; caused by a deficiency of riboflavin
    a condition caused by blocking the airways to the lungs (as with food or swelling of the larynx)
    a condition in which the vagina is unusually dry
    degenerative disorder
    condition leading to progressive loss of function
    a disorder in the sense of touch
    dysosmia, olfactory impairment, parosamia
    a disorder in the sense of smell
    condition in which swallowing is difficult or painful
    painful or difficult urination
    loss of ability to function normally
    an ill-defined state of irritability and distress
    adenosis, gland disease, glandular disease, glandular disorder
    a disorder of the glands of the body
    a condition characterized by excessive restlessness and movement
    impacted tooth, impaction
    a disorder in which a tooth is so crowded in its socket that it cannot erupt normally
    a disorder in which feces are impacted in the lower colon
    learning disability, learning disorder
    a disorder found in children of normal intelligence who have difficulties in learning specific skills
    (dentistry) a condition in which the opposing teeth do not mesh normally
    idiopathic disease, idiopathic disorder, idiopathy
    any disease arising from internal dysfunctions of unknown cause
    disturbance, folie, mental disorder, mental disturbance, psychological disorder
    (psychiatry) a psychological disorder of thought or emotion; a more neutral term than mental illness
    metabolic disorder
    a disorder or defect of metabolism
    nervous disorder, neurological disease, neurological disorder
    a disorder of the nervous system
    disorder in which serous fluid accumulates in a body sac (especially in the scrotum)
    sleep disorder
    a disturbance of the normal sleep pattern
    the condition of having respiration stopped by compression of the air passage
    haematocolpometra, hematocolpometra
    accumulation of blood in the vagina and uterus
    haematocolpos, hematocolpos
    accumulation of menstrual blood in the vagina (usually due to an imperforate hymen)
    defect of speech, speech defect, speech disorder
    a disorder of oral speech
    psilosis, sprue, tropical sprue
    a chronic disorder that occurs in tropical and non-tropical forms and in both children and adults; nutrients are not absorbed; symptoms include foul-smelling diarrhea and emaciation
    immunological disorder in which some part of the body's immune system is inadequate and resistance to infectious diseases is reduced
    lowering the body's normal immune response to invasion by foreign substances; can be deliberate (as in lowering the immune response to prevent rejection of a transplanted organ) or incidental (as a side effect of radiotherapy or chemotherapy for cancer)
    an inability to stay awake
    an inability to sleep; chronic sleeplessness
    pavor nocturnus, sleep terror disorder
    a disorder of sleep characterized by a dream of terrifying dimensions far worse than a typical nightmare; they occur during NREM sleep
    a prolonged disorder of eating due to loss of appetite
    an eating disorder, frequent in children, in which non-nutritional objects are eaten persistently
    binge-purge syndrome, binge-vomit syndrome, bulima nervosa, bulimarexia
    a disorder of eating in which the person alternates between strong craving for food and aversion to food; characterized by excessive eating followed by periods of fasting or self-induced vomiting
    binge-eating syndrome, bulimia
    a disorder of eating in which people go on eating binges and then feel guilt and depression and self-condemnation
    loss of the myelin covering of some nerve fibers resulting in their impaired function
    any degenerative disorder resulting from inadequate or faulty nutrition
    (dentistry) malocclusion in which the upper teeth extend abnormally far over the lower teeth
    excessive secretion of parathyroid hormone resulting in abnormally high levels of calcium in the blood; can affect many systems of the body (especially causing bone resorption and osteoporosis)
    inadequate secretion of parathyroid hormone resulting in abnormally low levels of calcium in the blood
    excessive activity of the pituitary gland (especially overactivity of the anterior lobe which leads to excess secretion of growth hormone)
    Asperger's syndrome
    a psychiatric disorder usually noted during early school years; characterized by impaired social relations and by repetitive patterns of behavior
    alcaptonuria, alkaptonuria
    a rare recessive metabolic anomaly marked by ochronosis and the presence of alkapton in the urine
    brain damage
    injury to the brain that impairs its functions (especially permanently); can be caused by trauma to the head, infection, hemorrhage, inadequate oxygen, genetic abnormality, etc.
    brain disease, brain disorder, encephalopathy
    any disorder or disease of the brain
    ataxia, ataxy, dyssynergia, motor ataxia
    inability to coordinate voluntary muscle movements; unsteady movements and staggering gait
    atopognosia, atopognosis
    absence or loss of topognosia; inability to locate correctly a point of touch
    abnormality in performing voluntary muscle movements
    MS, disseminated multiple sclerosis, disseminated sclerosis, multiple sclerosis
    a chronic progressive nervous disorder involving loss of myelin sheath around certain nerve fibers
    Parkinson's, Parkinson's disease, Parkinson's syndrome, Parkinsonism, paralysis agitans, shaking palsy
    a degenerative disorder of the central nervous system characterized by tremor and impaired muscular coordination
    any of several degenerative nervous disorders characterized by spasmodic movements of the body and limbs
    flaccid paralysis
    weakness or loss of muscle tone resulting from injury or disease of the nerves innervating the muscles
    impaired ability to learn grade-appropriate mathematics
    impaired ability to learn to write
    impaired ability to learn to read
    partial or total loss of articulate speech resulting from lesions of the central nervous system
    cardiopathy, heart disease
    a disease of the heart
    high blood pressure, hypertension
    a common disorder in which blood pressure remains abnormally high (a reading of 140/90 mm Hg or greater)
    abnormally low blood pressure
    ALS, Lou Gehrig's disease, amyotrophic lateral sclerosis
    thickening of tissue in the motor tracts of the lateral columns and anterior horns of the spinal cord; results in progressive muscle atrophy that starts in the limbs
    aneurism, aneurysm
    a cardiovascular disease characterized by a saclike widening of an artery resulting from weakening of the artery wall
    a continuous succession of slow, writhing, involuntary movements of the hands and feet and other body parts
    a progressive disease of the central nervous system marked by increasing lack of coordination and advancing to paralysis and death within a year of the appearance of symptoms; thought to have been transmitted by cannibalistic consumption of diseased brain tissue since the disease virtually disappeared when cannibalism was abandoned
    nerve compression
    harmful pressure on a nerve (especially in nerves that pass over rigid prominences); causes nerve damage and muscle weakness
    circulatory failure
    failure of the cardiovascular system to supply adequate amounts of blood to body tissues
    coronary failure, heart failure
    inability of the heart to pump enough blood to sustain normal bodily functions
    kidney failure, renal failure
    inability of the kidneys to excrete wastes and to help maintain the electrolyte balance
    Addison's disease, Addison's syndrome, hypoadrenalism, hypoadrenocorticism
    a glandular disorder caused by failure of function of the cortex of the adrenal gland and marked by anemia and prostration with brownish skin
    a glandular disease or enlargement of glandular tissue (especially of the lymph glands)
    aldosteronism, hyperaldosteronism
    a condition caused by overproduction of aldosterone
    Cushing's disease, hyperadrenalism
    a glandular disorder caused by excessive ACTH resulting in greater than normal functioning of the adrenal gland; characterized by obesity
    Cushing's syndrome, hyperadrenocorticism
    a glandular disorder caused by excessive cortisol
    hyperthyroidism, thyrotoxicosis
    an overactive thyroid gland; pathologically excessive production of thyroid hormones or the condition resulting from excessive production of thyroid hormones
    an underactive thyroid gland; a glandular disorder resulting from insufficient production of thyroid hormones
    reduction or lack of an immune response to a specific antigen
    inborn error of metabolism
    any of a number of diseases in which an inherited defect (usually a missing or inadequate enzyme) results in an abnormality of metabolism
    a disorder of lipid metabolism; abnormal levels of certain fats accumulate in the body
    lysine intolerance
    a disorder in which a lack of certain enzymes makes it impossible to digest the amino acid lysine
    a minor nonspecific ailment
    kinetosis, motion sickness
    the state of being dizzy or nauseated because of the motions that occur while traveling in or on a moving vehicle
    any of various disorders of lipoprotein and cholesterol metabolism that result in high levels of lipoprotein and cholesterol in the circulating blood
    any of various disorders of lipoprotein and cholesterol metabolism that result in low levels of lipoprotein and cholesterol in the circulating blood
    sleep apnea
    apnea that occurs during sleep
    anxiety disorder
    a cover term for a variety of mental disorders in which severe anxiety is a salient symptom
    psychosomatic disorder
    a mental disorder that causes somatic symptoms
    a disorder in one's mental state
    conversion disorder, conversion hysteria, conversion reaction
    a mental disorder characterized by the conversion of mental conflict into somatic forms (into paralysis or anesthesia having no apparent cause)
    a usually brief state of excitement and mental confusion often accompanied by hallucinations
    delusional disorder
    any mental disorder in which delusions play a significant role
    involuntary defecation not attributable to physical defects or illness
    folie a deux
    the simultaneous occurrence of symptoms of a mental disorder (as delusions) in two persons who are closely related (as siblings or man and wife)
    personality disorder
    inflexible and maladaptive patterns of behavior
    affective disorder, emotional disorder, emotional disturbance, major affective disorder
    any mental disorder not caused by detectable organic abnormalities of the brain and in which a major disturbance of emotions is predominant
    resembling schizophrenia but remaining within the bounds of normality
    neurosis, neuroticism, psychoneurosis
    a mental or personality disturbance not attributable to any known neurological or organic dysfunction
    aphonia, voicelessness
    a disorder of the vocal organs that results in the loss of voice
    flaccid bladder
    a urinary bladder disorder resulting from interruption of the reflex arc normally associated with voiding urine; absence of bladder sensation and over-filling of the bladder and inability to urinate voluntarily
    neurogenic bladder
    a urinary bladder disorder caused by a lesion in the nervous system
    spastic bladder
    a urinary bladder disorder resulting from spinal cord lesion or multiple sclerosis or trauma; absence of bladder sensation and incontinence and interrupted voiding of urine
    a speech disorder in which the same word is repeated several times in succession
    impaired articulatory ability resulting from defects in the peripheral motor nerves or in the speech musculature
    impaired ability to express ideas verbally; usually resulting from difficulties of reasoning (as in feeblemindedness or certain psychoses)
    speech disorder attributable to a disorder of phonation
    defective articulation of the `l' phoneme or the phoneme `r' is pronounced as `l'
    speech defect involving excessive use or unusual pronunciation of the phoneme `l'
    a speech defect that involves pronouncing `s' like voiceless `th' and `z' like voiced `th'
    stammer, stutter
    a speech disorder involving hesitations and involuntary repetitions of certain sounds
    dissociative disorder
    dissociation so severe that the usually integrated functions of consciousness and perception of self break down
    type of:
    physical condition, physiological condition, physiological state
    the condition or state of the body or bodily functions
  3. noun
    a disturbance of the peace or of public order
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    established customary state (especially of society)
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    anarchy, lawlessness
    a state of lawlessness and disorder (usually resulting from a failure of government)
    an unstable order
    disorder resulting from a failure to behave predictably
    riot, rioting
    a state of disorder involving group violence
    disorderliness, roughness, rowdiness, rowdyism
    rowdy behavior
    commotion, disruption, disturbance, flutter, hoo-ha, hoo-hah, hurly burly, kerfuffle, to-do
    a disorderly outburst or tumult
    discord, strife
    lack of agreement or harmony
    Sturm und Drang, turbulence, upheaval
    a state of violent disturbance and disorder (as in politics or social conditions generally)
    complete denial of all established authority and institutions
    demoralisation, demoralization
    a state of disorder and confusion
    noisy confusion and turbulence
    bedlam, chaos, pandemonium, topsy-turvydom, topsy-turvyness
    a state of extreme confusion and disorder
    a state of confusion
    schemozzle, shemozzle
    (Yiddish) a confused situation or affair; a mess
    convulsion, turmoil, upheaval
    a violent disturbance
    a disturbance that is extremely disruptive
    a public disturbance
    splash, stir
    a prominent or sensational but short-lived news event
    maelstrom, storm, tempest
    a violent commotion or disturbance
    storm center, storm centre
    a center of trouble or disturbance
    garboil, tumult, tumultuousness, uproar, zoo
    a state of commotion and noise and confusion
    agitation, ferment, fermentation, tempestuousness, unrest
    a state of agitation or turbulent change or development
    roller coaster
    anything characterized by abrupt and extreme changes (especially up and down)
    a turbulent state resulting in injuries and destruction etc.
    type of:
    the way something is with respect to its main attributes
  4. verb
    bring disorder to
    synonyms: disarray
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    bring order to or into
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    mess, mess up
    make a mess of or create disorder in
    derange, perturb, throw out of kilter
    throw into great confusion or disorder
    disturb the arrangement of
    jumble, scramble, throw together
    bring into random order
    randomise, randomize
    arrange in random order
    throw together in a confused mass
    type of:
    alter, change, modify
    cause to change; make different; cause a transformation
  5. verb
    disturb in mind or make uneasy or cause to be worried or alarmed
    synonyms: cark, disquiet, distract, perturb, trouble, unhinge
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    vex, worry
    disturb the peace of mind of; afflict with mental agitation or distress
    suggest fear or doubt
    eat, eat on
    worry or cause anxiety in a persistent way
    worry persistently
    type of:
    disturb, trouble, upset
    move deeply
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