unstable

1 not being in or able to maintain a state of balance the minute we put the books down on the unstable desk, the whole stack went crashing to the floor Synonyms unbalanced, unsteady Related Words rocky, shaky, tippy, tipsy, wavery, wobbly (also wabbly), wonky [British]; infirm, insecure, precarious, unsound; doddering, doddery, jiggling, jiggly, rickety, staggery, teetering, tottering, tottery; askew, awry, cockeyed, lopsided, off-kilter, uneven Near Antonyms even, level, straight; sound, sturdy, substantial Antonyms balanced, equilibrated, stabilized, stable, steady

2 likely to change frequently, suddenly, or unexpectedly financial investors don't like an unstable economy Synonyms capricious, changeable, changeful, flickery, fluctuating, fluid, inconsistent, inconstant, mercurial, mutable, skittish, temperamental, uncertain, unpredictable, unsettled, fickle, unsteady, variable, volatileRelated Words aimless, arbitrary, desultory, erratic, haphazard, hit-or-miss, irregular, random, scattered, slapdash, stray; ambivalent, hesitating, shaky, shilly-shally, shilly-shallying, vacillating, wavering; dicey, undependable, unreliable, untrustworthy; adaptable, mobile, protean, versatileNear Antonyms equable, even, uniform; abiding, durable, lasting, permanent, persistent; dependable, reliable, sure, tried, tried-and-true, true, trustworthy, trustyAntonyms certain, changeless, constant, immutable, invariable, predictable, settled, stable, stationary, steady, unchangeable, unchanging, unvarying

3 not staying constant unstable temperatures are not ideal storage conditions for wine Synonyms changing, erratic, fluctuating, irregular, unequal, uneven, unsteady, varyingRelated Words capricious, changeable, changeful, choppy, fickle, fluid, inconsistent, inconstant, mercurial, mutable, uncertain, unsettled, variable, volatileNear Antonyms regularAntonyms changeless, constant, stable, steady, unchanging, unvarying