Bun in his unit Share definition Flag The unexpected pregnancy of a homosexual man and his partner, whereas the man falls pregnant and no female is used. Guy 1 - Oh boy, is Bill getting fatter? Guy 2 - No way, he has a bun in his unit! Guy 1 - OMG!!! Bun in his unit by aussiedude85 June 10, 2011 0 0 Get merch Get the Bun in his unit mug. Buy Now — $32.95 See more merch