Bum Hum Share definition Flag Something that "hums" (stinks) which also comes from your bum. i.e farting..guffing, trumping...bottom vapours!!! "Hey what's that awful smell"It's Andy...he's got bum hum! Bum Hum by BFREASH February 17, 2010 0 0 Get merch Get the Bum Hum mug. Buy Now — $32.95 See more merch