To be unstable is to lack stability, meaning things could change without warning, like an unstable bookshelf that is likely to fall down. If you are unstable emotionally, you might be ecstatically happy one minute and horribly depressed and angry the next.

The adjective unstable means the opposite of stable. Stable is derived from the Latin base word stare meaning “to stand.” If a building, family, person, bridge, or chemical solution is stable it will “stand still,” even if something unexpected happens. On the other hand, if a person or thing is unstable and stress is applied, he, she, or it is likely to shift position, possibly in a dangerous way.

Definitions of unstable
  1. adjective
    subject to change; variable
    “everything was unstable following the coup”
    synonyms: fluid
    changeable, changeful
    such that alteration is possible; having a marked tendency to change
  2. adjective
    lacking stability or fixity or firmness
    unstable political conditions”
    “the tower proved to be unstable in the high wind”
    “an unstable world economy”
    likely to change frequently often without apparent or cogent reason; variable
    impermanent, temporary
    not permanent; not lasting
    coseismal, coseismic
    being where earthquake waves arrive simultaneously
    crank, cranky, tender, tippy
    (used of boats) inclined to heel over easily under sail
    explosive, volatile
    liable to lead to sudden change or violence
    rickety, shaky, wobbly, wonky
    inclined to shake as from weakness or defect
    liable to rock
    seismal, seismic
    subject to or caused by an earthquake or earth vibration
    unstable by being overloaded at the top
    (of structures or institutions) having lost stability; failing or on the point of collapse
    explosively unstable
    subject to change or variation
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    resistant to change of position or condition
    steadfast in purpose or devotion or affection
    lasting, permanent
    continuing or enduring without marked change in status or condition or place
    firm, steady, unfluctuating
    not liable to fluctuate or especially to fall
    lasting a long time without change
    (chemistry, physics, biology) resistant to change
    stabilised, stabilized
    made stable or firm
    not subject to change or variation especially in behavior
    show more antonyms...
  3. adjective
    affording no ease or reassurance
    synonyms: precarious, tenuous
    lacking a sense of security or affording no ease or reassurance
  4. adjective
    suffering from severe mental illness
    synonyms: mentally ill, unsound
    afflicted with or characteristic of mental derangement
  5. adjective
    disposed to psychological variability
    “his rather unstable religious convictions”
    uncertain how to act or proceed
  6. adjective
    highly or violently reactive
    “sensitive and highly unstable compounds”
    participating readily in reactions
Word Family

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