- to laugh so hard that you are not able to control yourself
- to double over from laughter
- The movie had everyone in the theatre in stitches.
- The comedian had the audience in stitches.
- My brother is always coming up with ways to prank our sister. He has me in stitches.
- I heard the best joke yesterday. It has me in stitches.
- Please come and watch the new hypnotist with us tomorrow night. She will have you in stitches.
A stitch is a stab of pain. It is generally used to describe a pain in your side from over exertion during exercise. It makes you bend over from pain, much the same as laughing can.
Although the precise idiom dates only from about 1930, Shakespeare had a similar expression in Twelfth Night (1601):
"If you desire the spleen, and will laugh yourselves into stitches, follow me."
The first available reference after that dates to 1914. A review published in The Lowell Sun read:
"There's a new face among the members in Ben Loring, a natural-born comedian, who seems to have no difficulty whatever in keeping his audience in stitches of laughter and glee."