Idioms can be a powerful linguistic tool only when they are used in the right way in the right places.
Idiom:
crackpot
Meaning:
an eccentric person with ideas that do not make sense to others, a crazy person
Example:
The man is a crackpot and you never know what he will do next.
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.