Fart Finger Share definition Flag a finger one shoves up their arsehole to induce farting. In order to let out some gas, John used the old Fart Finger and was able to let out a few rips for some relief. Fart Finger by Shit_4_Brains January 14, 2008 0 0 Get merch Get the Fart Finger mug. Buy Now — $32.95 See more merch