Synonyms and related words :
a bit thick, a bit thin, absurd, barred, beyond belief, closed-out, contrary to reason, doubtable, doubtful, dubious, dubitable, excluded, extraordinary, hard of belief, hard to believe, hopeless, illogical, implausible, impossible, improbable, incomprehensible, inconceivable, incredible, laughable, logically impossible, ludicrous, mind-blowing, mind-boggling, not deserving belief, not possible, open to doubt, open to suspicion, oxymoronic, paradoxical, passing belief, preposterous, problematic, prohibited, questionable, rare, ridiculous, ruled-out, self-contradictory, singular, staggering belief, suspect, suspicious, tall, thick, thin, unacceptable, unbelievable, uncommon, unconvincing, unearthly, ungodly, unimaginable, unique, unlikely, unordinary, unusual, unwonted, unworthy of belief