arse-up noun 1arse up verb 1forms 4 noun1 •(slang, vulgar) A mistake or blunder; a cock-up. arse up verb1 •(UK, slang) To mess up; to botch.Take aim. Throw. If he arsed it up and made the creature angry – ha, well. He didn't look scared though. — 2011 formsarsed up · arsing up · arses up · arse-ups
