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.
one foot in the grave
The woman has one foot in the grave and is not expected to live much longer.
List of common idioms, their meanings and examples of their usage in sentences
Idioms can be a powerful linguistic tool only when they are used in the right way in the right places.