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.
hook, line and sinker
without question or doubt, completely
The girl fell in love with her new boyfriend hook, line and sinker.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is a group of words, or in other words, a phrase that has a meaning other than its literal meaning of the words in it.