SIDESPLITTING

killing, sidesplitting

(adjective) very funny; “a killing joke”; “sidesplitting antics”

Source: WordNet® 3.1

Etymology

Adjective

sidesplitting (comparative more sidesplitting, superlative most sidesplitting)

(of laughter) Intensely uncontrollable and genuine.

Exceptionally funny; hilarious.

Source: Wiktionary