|1.||tastes like butt|
When something tastes so vile, so disgusting, so repugnant, that it can be compared to what a butt might taste like.
(Of course, most people don't taste butts, so a better phrase would be "what a butt smells like." Or, perhaps, what the expulsion of methane from out of the butt smells like.)
This banana peel tastes like butt.