bio boy Share definition Flag A biological boy or male. Usually used in refence to trans people, such as a maleto female trans-woman or female-to male trans-man. I'm a bio-boy! Or Do you think I'm a bio boy or a tranny? bio boy by be-bop-a-lula February 2, 2005 0 0 Get merch Get the bio boy mug. Buy Now — $32.95 See more merch