3 letter man Share definition Flag WWII Navy slang meaning FAG, a term used on the battleship USS Texas and possibly other navy ships. Seamen First Class Benjamin Dover is a strong 3 letter man who swabs the poopdeck. 3 letter man by K Werz. February 11, 2008 0 0 Get merch Get the 3 letter man mug. Buy Now — $32.95 See more merch