Arse
British SlangDefinition
Vulgar British slang: the buttocks; by extension, a contemptible or foolish person or “nonsense,” and in verb use, to waste time or spoil something.
Examples
"He slipped on the ice and landed on his arse."
"You’re talking out of your arse; the train doesn’t even stop there on Sundays."
"He really arsed up the presentation by forgetting the slides."