Pronunciation IPA (key): /ˈluːni/ Audio (CA)(file) Adjective Positive loony Comparative loonier Superlative looniest (informal) If someone is loony, he or she is an insane person. Synonym: crazy Noun Singular loony Plural loonies (informal) A loony is an insane or foolish person. Synonym: crazyWikiwand - on Seamless Wikipedia browsing. On steroids.Remove ads