flenniken Share definition Flag Slang for an individual especially a descendant of irish heritage prone to chasing red flags. Someone who has no morals. Thats a real Flenniken thing to do, i heard the one hes chasing is a bit crazy. flenniken by Trooperdaddy July 7, 2022 0 0 Get merch Get the flenniken mug. Buy Now — $32.95 See more merch