fbmb Share definition Flag Slang acronym for "first base my boner". otherwise known as a blow job. I got so fed up with this girl giving me a terrible hand job that i finally said "will you first base my boner (fbmb)instead?" fbmb by fbmb king January 6, 2008 0 0 Get merch Get the fbmb mug. Buy Now — $32.95 See more merch
