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:
nose around
Meaning:
to look for something kept private or secret, to pry into something
Example:
The secretary nosed around her boss's desk to look for the address.
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.