Abbreviation for Bird Trouble which expresses your significant other giving you grief. Every man with a partner experiences some form of BT (some worse than others) The term derives from track 3 "Bird Trouble" on UK Street Punk/Oi! Band Cock Sparrers 1994 album Guilty As Charged.
I can't go out tonight. My girl's giving me BT and I gotta deal with this shit!