Polari is a secret slang language that was mainly used by the gay and queer scene in the UK during the 20th century, particularly when homosexuality was criminalized. It wasn't ever written into a full language, but it became a shared collection of words and phrases that allowed the queer community to communicate safely in public without being understood and discriminated against by others.

It thrived in spaces like gay/lesbian clubs, drag shows, and the theatre scenes. It evolved from older slang, used by travelling enertainers, fairground workers, sailors, theatre workers, and sex workers. Words from Italian, French, rhyming slang, back slang, American military slang, and criminal cant were adopted into the ever evolving language.

There are around 500 known Polari words, but most people only know a small number, many not even knowing what is or isn't considered Polari.