Short for Black Wing Lair. A high level instance in WoW, (world of warcraft), filled with various high level epics that no one but the big guilds and clans are able to obtain.
That guild Eminence has run BWL so many times that all of their characters have their tier-2 epic sets.
Acronym for "bursting with laughter."
Person 1: "I am a smart guy."
Person 2: "BWL"