THESAURUS
improbable
absurd, crazy, distant, doubtable, doubtful, dubious, dubitable, extraordinary, fanciful, farfetched, fishy, flimsy, forced, hard to believe, hardly possible, implausible, impossible, inconceivable, incredible, insane, ludicrous, mad, more than doubtful, more than expected, out-of-the-way, past expectation, peculiar, questionable, quite another thing, remote, ridiculous, something else again, strained, strange, sudden, thin, unannounced, unanticipated, unbelievable, unconvincing, undivined, unexpected, unforeseeable, unforeseen, unguessed, unheralded, unhoped for, unlikely, unpredictable, unpredicted, unprepared for, unpromising, unrealistic, unsubstantial, unthinkable, weak, weird, wild, without warning
ROGET THESAURUS
improbable
Improbability
N
improbability, unlikelihood, unfavorable chance, bad chance, ghost of a chance, little chance, small chance, poor chance, scarcely any chance, no chance, bare possibility, long odds, incredibility,
improbable, unlikely, contrary to all reasonable expectation, wild, far out, out of sight, outtasight, heavy, rare, unheard of, inconceivable, unimaginable, inimaginable, incredible, more than doubtful, strange, bizarre (uncomformable), the chances are against, aquila non capit muscas, pedir peras pal olmo.