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:
out of all proportion
Meaning:
of an exaggerated proportion
Example:
The complaints of the students were out of all proportion to what the problem was.
List of common idioms, their meanings and examples of their usage in sentences
The language peculiar to a people or to a district, community, or class