Fat dammit! Share definition Flag Adjective used in place of a more crude phrase. Derives from Fat Bastard. Fat dammit! That guy just cut me off, so I couldn't get off the ramp to merge properly. That Fat Bastard! Fat dammit! by Toxic Ink October 8, 2008 0 0 Get merch Get the Fat dammit! mug. Buy Now — $32.95 See more merch