Form of online speak used in a forum, short for "Ban This Idiot". Used when a poster on a forum talks or behaves in such a manner that he or she merits being banned to prevent other users from having to put up with such idiocy again.
Poster 1: hey u all sux so much why u use this lame forum?
BTI is the chillest TTC member, should have won coolest member, has a very large penis, is a class act, and ran a train on Jimmy's mother. Also known for having a mother who is a friend of the TTC and is a ROBLOX Youtuber.
Person 1: OMG! It's BTI!
Person 2: No way? That's the dude who had sex with Jimmymom!