An idiom is a group of words, or in other words, a phrase that has a meaning other than its literal meaning of the words in it.
Idiom:
take the Fifth
Meaning:
to hide behind the Fifth Amendment of the United States Constitution which guarantees any witness the right not to incriminate himself or herself while testifying at a trial
Example:
The man decided to take the Fifth rather than tell all of the facts at the trial.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is defined as - a group of words in a fixed order that has a particular meaning that is different from the meanings of each word on its own.