Mouldy ass Share definition Flag when you don't wipe your ass & it forms a layer of mould in your ass crack, which smells & makes other people gag when they walk past. Oh my god the seat smells, the last person who sat here must have had mouldy ass. Mouldy ass by Sami D December 9, 2008 0 0 Get merch Get the Mouldy ass mug. Buy Now — $32.95 See more merch