expression, na-adjective, noun
Describes a person who acts like they know everything, often in a cheeky or impertinent way. Used as a noun or adjectival noun (e.g., 利いた風な口をきく).
彼はいつも利いた風なことを言う。
He always says know-it-all things.
利いた風な口をきくんじゃない。
Don't talk so cheekily.
From 利いた (past form of 利く 'to be effective, clever') + 風 'manner, air'. The alternate spelling 聞いた風 uses 聞く 'to hear', suggesting a know-it-all attitude based on hearsay. The exact origin is uncertain, but it likely emerged as a set phrase describing someone who acts clever or well-informed.