Laughing My ButtLaughing My Butt/Bum/Balls Off, an slang expression (see LOL)
Overall, the abbreviation LMBO stands for laughing my butt off.
LMAO is an acronym that stands for Laughing My Ass Off. Many people say (or text) this acronym when they find something particularly funny. Sometimes, when a person finds something extremely funny, they say LMFAO.
Following her emotional breakdown, Azula was put in a mental health facility to recover, though she eventually joined Team Avatar on their search for Ursa, as part of her secret agenda to betray them and usurp the throne from Zuko. Sometime after her exile, Azula returned to the Fire Nation Capital in secret.
Zuko was clearly far from being pleased with his sister for her actions but did not seem to show much resentment for that, even commenting he actually felt good for her restored mentality.