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.
rotten to the core
to be completely no good and worthless
The local government was rotten to the core and everyone was happy when they were voted out of office.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is a widely used saying or expression containing a figurative meaning that differs from the phrase's literal meaning.