What is LMAO?
LMAO is an acronym for ‘laughing my ass off’, an internet slang that is used to convey hilarity or exaggerated mirth. LMAO is usually used in chat rooms or in instant messaging (Yahoo!, MSN, etc), but it has also found its way into forums, emails and even in text messaging. LMAO belongs in the same league as other internet slang acronyms such as LOL (laugh out loud or laughing out loud) ROFL (rolling on the floor laughing) or the combination ROFLMAO (rolling on the floor laughing my ass off).
Nobody really knows for sure where the acronym came from or how it started, but many believe that it was popularized during the time of earlier chat platforms such as Pirch and m-Internet Relay Chat (mIRC). Analog smiley faces were not enough to convey a sense of hilarity, and typing the whole phrases describing hilarity is time consuming (at least as a reaction in a fast paced chat room), thus the acronyms describing hilarity such as LMAO were born.