Anything that makes you laugh out loud can be described as sidesplitting. If you are a stand-up comedian, your dream is to tell one sidesplitting joke after another.
If you've ever laughed so hard that tears streamed down your face, or so uproariously that you nearly fell out of your chair, you know what sidesplitting means. This informal adjective is perfect for describing that kind of laughter. Originally spelled with a hyphen, side-splitting, and defined as "affecting with compulsive laugher," it first appeared around 1820.