Antonyms of adj sidesplitting

1 sense of sidesplitting

Sense 1
killing, sidesplitting -- (very funny; "a killing joke"; "sidesplitting antics")

INDIRECT (VIA humorous) -> humorless, humourless, unhumorous -- (lacking humor; "it was a humorless wink; a wink of warning"- Truman Capote)

Similarity of adj sidesplitting

1 sense of sidesplitting

Sense 1
killing, sidesplitting -- (very funny; "a killing joke"; "sidesplitting antics")
       => humorous (vs. humorless), humourous -- (full of or characterized by humor; "humorous stories"; "humorous cartoons"; "in a humorous vein")