[1] : WordNet (r) 2.0

unpredictable
     adj 1: impossible to foretell ant: predictable
     2: unknown in advance; "an unpredictable or indeterminable
        future"
     3: not occurring at expected times syn: irregular
see also:
predictable irregular 

[2] : Moby Thesaurus II by Grady Ward, 1.0

148 moby thesaurus words for "unpredictable":
   accidental, adrift, adventitious, afloat, agnostic, aleatory,
   alternating, ambiguous, amorphous, capricious, casual, causeless,
   chance, chancy, changeable, changeful, contingent, coquettish,
   destinal, desultory, deviable, dicey, dizzy, doubtful, doubting,
   dubious, eccentric, equivocal, erratic, extraordinary, faddish,
   fast and loose, fatal, fatidic, fickle, fitful, flickering,
   flighty, flirtatious, flitting, fluctuant, fluctuating, fluky,
   fortuitous, freakish, giddy, hesitant, hesitating, iffy, impetuous,
   improbable, impulsive, incalculable, incidental, inconsistent,
   inconstant, indecisive, indemonstrable, indeterminate, infirm,
   insecure, irregular, irresolute, irresponsible, light, mazy,
   mercurial, moody, more than expected, out-of-the-way,
   past expectation, polysemous, quicksilver, rambling, restless,
   risky, rocky, roving, scatterbrained, shaky, shapeless, shifting,
   shifty, shuffling, skeptical, skittish, spasmodic, spineless,
   sudden, tottery, touch-and-go, toying, treacherous, unaccountable,
   unannounced, unanticipated, uncaused, uncertain, unconfirmable,
   uncontrolled, unconvinced, undependable, undetermined,
   undisciplined, undivinable, undivined, unexpected, unfixed,
   unforeseeable, unforeseen, unguessed, unhealthy, unheralded,
   unhoped for, unlooked-for, unpersuaded, unpredicted,
   unprepared for, unprovable, unreliable, unrestrained, unsafe,
   unsettled, unsound, unstable, unstable as water, unstaid,
   unsteadfast, unsteady, unsure, untrustworthy, unverifiable,
   vacillating, vagrant, variable, versatile, vicissitudinary,
   vicissitudinous, volatile, wandering, wanton, wavering, wavery,
   wavy, wayward, whimsical, wishy-washy, without warning

Unpredictable >> U Words
Unpredictable, definition of term: Unpredictable
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