Acronym for "Better Be Hitting That" or "Best Be Hitting That."
Best used when one of your friends is talking to a girl (whether good looking or ugly). It can be used in any situation where someone is talking to same or opposite sex.
(While your friend is talking to a hideous looking girl)
You: "Hey Bob B.B.H.T."
Bob: "Aww fuck you!"
Ugly girl: "What does that mean?"
Bob: "I better be hurrying this up"