Thigh-slapper is a term used to describe something that is extremely funny. If you're writing a story or a speech and you want to avoid using the word "thigh-slapper", there are several alternatives you can use. You could describe something as hilarious, side-splitting, knee-slapping, rib-tickling, or gut-busting. If you're looking for something a little more colorful, you could try "laugh-out-loud funny", "roaringly funny", "belly-aching funny", or "tear-inducing funny". Whatever word you choose, be sure to use it in context to ensure that your audience understands just how funny you find something.