Specifically, a particular variety of language; a restricted dialect used in a given historical period, context etc.
An artistic style (for example, in art, architecture, or music); an instance of such a style.
An expression peculiar to or characteristic of a particular language, especially when the meaning is illogical or separate from the meanings of its component words.
(programming) A programming construct or phraseology that is characteristic of the language.
“There's an idiom in Tennessee that says a fooled man can't get fooled again.”
“The few reviews written in a public idiom whether in literary journals or the general press are increasingly characterized by their blandly uncritical quality.”
“In these depictions, done in a Western representational idiom, everything is explicit, and there are no secrets.”