implausible
unpersuasive
a bit thick
a bit thin
absurd
beyond belief
doubtable
doubtful
dubious
dubitable
flimsy
hard of belief
hard to believe
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
bemused
convince
dissimilar
distasteful
halfhearted
illogical
impractical
inconclusive
ineffective
inept
ironic
rueful
self-deprecating
unfitted
uninterested
uninteresting
unreal
unsatisfactory
unsatisfying
unsure
untenable
untrue
convincing
mincing
rinsing
wincing
cogent
impressive