What do you call a person who speaks 4 languages?

There isn't a specific, commonly used word for someone who speaks four languages. However, you could use the following terms:

* Quadrilingual: This is the most accurate and formal term, meaning "speaking four languages."

* Polyglot: This is a general term for someone who speaks multiple languages, and it can be used for anyone who speaks more than two.

* Fluent in four languages: This is a straightforward and easy-to-understand description.

Ultimately, the best term depends on the context and the level of formality you want to achieve.