F you in the A Share definition Flag A term that describes anal sex. An abbreviation of fuck you in the ass. 1. Oi Luke Martin, you're a cunt. 2. What? I'm gunna F you in the A for that. F you in the A by Asuina February 24, 2008 0 0 Get merch Get the F you in the A mug. Buy Now — $32.95 See more merch