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.
queer as a three-dollar bill
to be very strange
The woman is the strangest person that I have ever met. She is as queer as a three-dollar bill.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is defined as - a group of words whose meaning is different from the meanings of the individual words.