From Longman Dictionary of Contemporary Englishloonyloon‧y1 /ˈluːni/ noun (plural loonies) [countable] informalCRAZY someone who is crazy or strange Her brother’s a complete loony.
Examples from the Corpus
loony• He said I waved at the poor man like a loony.• Janet's brother is a complete loony.• Two young lads from Hafnarfjödur, a small fishing village near Reykjavik, were going like loonies.• I would only trash incoming mail from obvious opponents and obvious loonies.• Political loony, surprised thief, old lag with a grudge ... it's facts I want, not surmise.• She felt like a total loony doing these things for herself.• He's an absolute utter loony.loonyloony2 adjective informal silly, crazy, or strange a loony ideaExamples from the Corpus
loony• What kind of a loony bin have they got down there in Berkeley, anyway?• They felt free to festoon the machine with all sorts of loony filigrees.• What of the loony fringe that I had so conveniently forgotten?• I can't be loony if I can remember my dream, surely?• Major was spot on, just as he was dead right to go on to warn Hague against his loony right.Origin loony1 (1800-1900) lunatic 