An expression in the usage of a language that is peculiar to itself either in having a meaning that cannot be derived from the conjoined meanings of its elements or in its grammatically atypical use of words.
Idiom:
join the fray
Meaning:
to join a fight or argument
Example:
I did not want to join the fray and argue with the other members of the group.
List of common idioms, their meanings and examples of their usage in sentences
Idioms are phrases which cannot be understood simply by looking at the meaning of the individual words in the phrase.