BTFRB Share definition Flag Adj. Shorted slang word used on AIM, meaning- Be the Fuck Right Back, which mean stop fucking talking to me and leave me alone before i throw something at your face. A: dude ur fat and stupid B: i hate u so much A: good B: BTFRB BTFRB by Snarski November 13, 2005 0 0 Get merch Get the BTFRB mug. Buy Now — $32.95 See more merch