idiom; set phrase; idiomatic phrase
Refers to a fixed expression whose meaning is not predictable from its parts, or a conventional phrase used as a unit.
Often used for traditional sayings or proverbs that convey wisdom or advice.
"Abura o uru" is a Japanese idiom.
"Isogaba maware" is a well-known proverb.
成句 is a slightly more formal term for a fixed set phrase, close in meaning to 熟語 when it means 'idiom'.
Chinese four-character phrase or idiomatic expression
From 成 (sei, 'become, form') + 句 (ku, 'phrase, clause'), literally 'formed phrase'.