A phrase many people (you) use when you think something is funny. Even though, your staring at you phone screen with a nuetral face. Lmao is used mostly when texting, and annoying 12 year olds mostly use this phrase.
Lmao is an abbreviated term for "Let's meet at once ."
Often used by drug dealers & criminals as a secret code, be weary of this term as it can mean that a person is trying to meet with you and probably has bad intentions.