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:
card up one's sleeve
Meaning:
a plan or argument that is kept back to be used later if needed
Example:
I think that our boss has a card up his sleeve and he will help us later.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is defined as - a group of words in a fixed order that has a particular meaning that is different from the meanings of each word on its own.