Synonyms and related words :
a bit thick, a bit thin, absurd, beyond belief, doubtable, doubtful, dubious, dubitable, flimsy, hard of belief, hard to believe, implausible, improbable, inconceivable, incredible, not deserving belief, open to doubt, open to suspicion, passing belief, preposterous, problematic, questionable, ridiculous, staggering belief, suspect, suspicious, tall, thick, thin, unbelievable, unearthly, ungodly, unimaginable, unsubstantial, unthinkable, unworthy of belief, weak