"Thigh slapper" is a term used to describe something that is extremely funny or amusing. Synonyms for this term include "belly laugh," "gut-buster," "knee-slapper," "side-splitter," "ripping yarn," "hilarious story," and "riotous tale." These words all convey a sense of uproarious laughter and mirth, and are often used in casual conversation or in reviews of comedy shows, movies, or books. Whether you are looking for a way to describe a particularly funny joke, an amusing anecdote, or a hilarious comedy routine, using one of these synonyms for "thigh slapper" can help you to convey the sense of humor and levity that the situation or performance elicited.