Mark: Hey, look at this dumb cat picture https://imgur.com/gallery/vCVqN Sam: LOL ! Sam: Hey Tom, look at this dumb cat picture. I lol’d so hard! https://imgur.com/gallery/vCVqN Tom: Ha, yeah, good pic. It’s never used in formal writing and has a few slightly different forms. Sometimes people also say lolz, which is like trying to make it plural in a strange way.

Laugh out loud. Used as a shorthand when you want to say that something is very funny.

laughing out loud; overused on your internets