Irregular describes something that's unpredictable or uneven. If your dog has irregular spots, it means that she has random splotches of color scattered across her fur.

Anything that doesn't have a pattern or schedule is irregular, like the irregular hours of a store that's only open when the owner feels like it. In grammar, an irregular part of speech is one that doesn't stick to the usual rules. Irregular can also describe something doesn't meet standards, like irregular clothing that's sold at a discount. Irregular originally meant "not in conformity with Church rules."

Definitions of irregular
  1. adjective
    (of a surface or shape); not level or flat or symmetrical
    “walking was difficult on the irregular cobblestoned surface”
    not even or uniform as e.g. in shape or texture
  2. adjective
    (of solids) not having clear dimensions that can be measured; volume must be determined with the principle of liquid displacement
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    (of solids) having clear dimensions that can be measured; volume can be determined with a suitable geometric formula
  3. adjective
    falling below the manufacturer's standard
    irregular jeans”
    not perfect; defective or inadequate
  4. noun
    merchandise that has imperfections; usually sold at a reduced price without the brand name
    synonyms: second
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    type of:
    merchandise, product, ware
    commodities offered for sale
  5. adjective
    deviating from normal expectations; somewhat odd, strange, or abnormal
    “highly irregular behavior”
    synonyms: atypical
    abnormal, unnatural
    not normal; not typical or usual or regular or conforming to a norm
  6. adjective
    contrary to rule or accepted order or general practice
    irregular hiring practices”
    prohibited by law or by official or accepted rules
    asymmetrical, crooked
    irregular in shape or outline
    casual, occasional
    occurring from time to time
    improper, unconventional, unlawful
    not conforming to legality, moral law, or social convention
    randomised, randomized
    set up or distributed in a deliberately random way
    of verbs not having standard (or regular) inflection
    unrhythmic, unrhythmical
    not rhythmic; irregular in beat or accent
    rough, unsmooth
    having or caused by an irregular surface
    subject to change or variation
    asymmetric, asymmetrical
    characterized by asymmetry in the spatial arrangement or placement of parts or components
    lacking systematic arrangement or method or organization
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    in accordance with fixed order or procedure or principle
    of members of a team; not substitutes
    lawful, rule-governed
    according to custom or rule or natural law
    official, prescribed
    conforming to set usage, procedure, or discipline
    standard, stock
    regularly and widely used or sold
    regularly spaced in time
    evenly spaced
    (used of verbs) having standard (or regular) inflection
    ordered well
    rhythmic, rhythmical
    recurring with measured regularity
    symmetric, symmetrical
    having similarity in size, shape, and relative position of corresponding parts
    characterized by order and planning
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  7. adjective
    lacking continuity or regularity
    “an irregular worker”
    synonyms: temporary
    part-time, parttime
    involving less than the standard or customary time for an activity
  8. adjective
    not occurring at expected times
    synonyms: unpredictable
    recurring in scattered and irregular or unpredictable instances
  9. adjective
    independent in behavior or thought
    “she led a somewhat irregular private life”
    synonyms: maverick, unorthodox
    not conforming to accepted rules or standards
  10. noun
    a member of an irregular armed force that fights a stronger force by sabotage and harassment
    synonyms: guerilla, guerrilla, insurgent
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    Maquis, Maquisard
    a guerrilla fighter in the French underground in World War II
    urban guerrilla
    a guerrilla who fights only in cities and towns
    type of:
    someone engaged in or experienced in warfare
  11. adjective
    (used of the military) not belonging to or engaged in by regular army forces
    irregular troops”
    irregular warfare”
    partisan, partizan
    devoted to a cause or party
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    (used of the military) belonging to or engaged in by legitimate army forces
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