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:
sit bolt upright
Meaning:
to sit up straight
Example:
I sat bolt upright when I heard the news about my cousin.
List of common idioms, their meanings and examples of their usage in sentences
The language peculiar to a people or to a district, community, or class