It's an ideas generator for writers. Give it a word and it returns a list of related phrases.
The Thesaurus is a great way to come up with phrases and sayings connected to the topic you are writing about - often ones you would never have thought of.
The Phrase Thesaurus is used by professional journalists, copywriters and songwriters, or anyone interested in words and phrases.
There are two ways to use it, either:
Search for phrases that are related in some way to your word.
Search for phrases that contain your word.