An idiom is a widely used saying or expression containing a figurative meaning that differs from the phrase's literal meaning.
Idiom:
touch a sore spot/point
Meaning:
to mention a sensitive matter that will upset someone
Example:
I touched a sore spot when I began to talk about my friend's problems at work.
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.