UNSTABLE

adj. 1 changeable, variable, unsteady, inconstant, inconsistent, insecure, capricious, fickle, irregular, unpredictable, unreliable, erratic, volatile, fluctuating, flighty, mercurial, vacillating, tergiversating, indecisive, undecided, irresolute, indefinite, unsettled He seems too unstable to maintain a long-standing relationship 2 See unsound, 1, above.