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:
armed and dangerous
Meaning:
to have a weapon that may be used (usually used for a criminal)
Example:
The criminal was armed and dangerous when the police arrested him.
List of common idioms, their meanings and examples of their usage in sentences
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.