implausible
This is an implausibly upbeat story.
The soldiers in the movie are implausibly well-groomed.
The plot relies on her implausibly rejecting an opportunity to escape.
They argue, not implausibly, that these decisions would have had to be taken anyway.
He denied - implausibly, some say - that there was a feud.

SMART Vocabulary: related words and phrases

Impossible and improbable
apt
aptness
be out of the questionidiom
be pissing in the windidiom
beggar
flimsily
flimsiness
goodbye
goodbye to somethingidiom
hopeless case
impenetrably
nail
nohow
not a chance
not have a snowball's chance in hellidiom
one in a millionidiom
pig
piss
snowball
unicorn

You can also find related words, phrases, and synonyms in the topics:

Not believable