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.
hang (someone) in effigy
to hang a dummy of a hated person
The demonstrators hung the dishonest politician in effigy.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is a type of phrase or expression that has a meaning that can't be deciphered by defining the individual words.