Literally, the acronym stands for "Bu Guai Bad Kid", a phrase used to describe a very badly misbehaving child, or, by extension, someone who has jokingly wronged you.
The first two words are pinyin versions of the Chinese for "misbehaving", which, along with the "bad kid" half of the phrase, expresses the extreme misbehavior of said person.
Dude, that guy has owed me lunch for almost a year now. What a freaking BGBK.
by r4wr89 December 6, 2010
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