improbable vs unconvincing

improbable and unconvincing both are adjectives.

Word	Noun	Adjective	Verb	Adverb
improbable	No	Yes	No	No
unconvincing	No	Yes	No	No

As adjectives, improbable and unconvincing are synonyms defined as:

improbable and unconvincing: having a probability too low to inspire belief

Other synonyms of improbable include unbelievable, unlikely.

improbable (adjective)	unconvincing (adjective)
not likely to be true or to occur or to have occurred	not convincing
having a probability too low to inspire belief	having a probability too low to inspire belief
too improbable to admit of belief