- laughing my ass off; laughed my ass off.
Origin of LMAO
from its use in digital communications
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Word Origin and History for lmao
by 1997, online abbreviation of laughing my ass off. Related: LMFAO (by 2000).
Online Etymology Dictionary, © 2010 Douglas Harper