1. (音乐、舞蹈、建筑的)风格，特色
    A particular idiom is a particular style of something such as music, dance, or architecture.

    e.g. McCartney was also keen to write in a classical idiom, rather than a pop one...
           麦卡特尼也热衷于古典风格而不是通俗风格的创作。
    e.g. It was an old building in the local idiom.
           那是一座具有当地风格的古建筑。

2. 习语;成语
    An idiom is a group of words which have a different meaning when used together from the one they would have if you took the meaning of each word separately.

    e.g. Proverbs and idioms may become worn with overuse...
           谚语和习语会由于使用过多而变得俗套。
    e.g. She is, in fact, a perfect illustration of the French idiom 'to be comfortable in one's own skin.'
           实际上，她很好地诠释了“欣然接纳自我”这一法语习语的意思。

3. 方言;土语
    Idiom of a particular kind is the language that people use at a particular time or in a particular place.

idiom的近义词

    e.g. And nothing was so irritating as the confident way he used archaic idiom.
           没什么比他使用过时的方言时那种自负的神态更气人的了。
    e.g. ...her command of the Chinese idiom.
           她对汉语方言的掌握