Answer:
An idiom
Explanation:
An idiom is a group of words which have a different meaning when used as a group than individually.
For example, saying, "Get off my back!" does not mean that someone is literally on your back but it means the person should stop bothering you.
From the phrase, "The sea captain was an old salt" does not mean that he is a salt but it means that he is a veteran sailor who has sailed for many years.
