improbable
unbelievable
unconvincing
unlikely
a bit thick
a bit thin
absurd
beyond belief
debatable
doubtable
doubtful
dubious
dubitable
fishy
flimsy
hard of belief
hard to believe
hardly possible
inconceivable
incredible
more than doubtful
not deserving belief
open to doubt
open to suspicion
passing belief
preposterous
problematic
puzzling
questionable
ridiculous
staggering belief
suspect
suspicious
tall
thick
thin
unearthly
ungodly
unimaginable
unpromising
unreasonable
unsubstantial
unthinkable
unworthy of belief
weak
chimerical
coincidental
dissimilar
farfetched
impractical
inaccurate
inconclusive
irreconcileable
out-of-touch
reliant
repugnant
stagey
suggestible
uncalled
unconvinced
unfitted
unproved
unrealistic
unsurprised
untenable
untrustworthy
plausible