There are countless synonyms for the phrase "laugh one's head off." Some of the most popular ones include "die laughing," "crack up," "split a gut," "burst out laughing," and "roar with laughter." Other options include "burst into fits of giggles," "be convulsed with laughter," "howl with mirth," "be in stitches," and "guffaw loudly." Whether you're describing a hilarious joke, a silly prank, or a ridiculous situation, these synonyms are perfect for adding some fun and flavor to your writing or conversation. So go ahead and use them to express yourself and make others laugh too!