LM3O Posted in L Best definition LM3O Laughing my balls off. 3 is a pair of sideways balls; a sack; a sackful, if you will. “Man, every time Steve speaks I LM3O. LM3O!” How satisfied are you with the definition? Looking for LM3O meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 97 times.