40 floz Share definition Flag Slang. Short for 40 fluid ounces. Written on the bottle as 40 fl. oz. but pronounced as one whole word. origin: Oakland bitch! "What you drankin on patna?" "I'm sippin on that Ol' English 40 floz playboy! 40 floz by FleetWood72 from the B.N.C. October 18, 2006 0 0 Get merch Get the 40 floz mug. Buy Now — $32.95 See more merch