An Idiom

1. A manner of speaking, a mode of expression peculiar to a language, person, or group of people.
2. A language or language variety; specifically, a restricted dialect used in a given historical period, context etc.
3. An established expression whose meaning is not deducible from the literal meanings of its component words, often peculiar to a given language.
4. An artistic style (for example, in art, architecture, or music); an instance of such a style.
5. (programming) A programming construct or phraseology that is characteristic of the language.

Synonyms

• (language variety): lect, languoid, dialect(loosely), vernacular (loosely), language(loosely)
• (phrase): expression (loosely), form of words (loosely), phrase (loosely), locution(loosely)