assius fallius Share definition Flag A rare condition in which an individual's butt falls off randomly. Insanely rare. Very painful. Fob, my friend has assius fallius, his butt falls off randomly all the time. assius fallius by Fobm4ster May 3, 2021 0 0 Get merch Get the assius fallius mug. Buy Now — $32.95 See more merch