IPA: //ʌnˈhjuːmərəs//
KK: /ʌnˈhjuːmərəs/
Not funny or lacking in humor.
The movie was so unhumorous that the audience didn't laugh at all.
Unhumorous → It is formed from "un-" (meaning not) and "humorous" (from Latin "humor", meaning fluid or mood, which evolved to mean funny or comical). The word "unhumorous" means not funny or lacking humor.
Think of 'not' ('un-') being added to 'funny' ('humorous') — that's why unhumorous means something that is not funny.