An idiom is defined as - a group of words whose meaning is different from the meanings of the individual words.
Idiom:
out of line
Meaning:
unacceptable, not correct
Example:
The salesman's proposal to travel to New York is out of line. We can never accept it.
List of common idioms, their meanings and examples of their usage in sentences
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.