unconvincing
Definitions
Failing to persuade or satisfy the mind that something is true or valid.
Lacking the qualities necessary to inspire belief or confidence.
Examples
The suspect's alibi was completely unconvincing to the detectives.
Her explanation for being late was so unconvincing that nobody believed her.
Synonyms
implausible unpersuasive dubious questionable flimsy far-fetched incredulous
Antonyms
convincing persuasive plausible credible believable compelling cogent