Formal:
* Pentaglot: This is the most common and accurate term, meaning "someone who speaks five languages."
* Polyglot: This term is used for someone who speaks multiple languages, but doesn't specify a number.
* Multilingual: This term simply means "speaking multiple languages" and is not specific to a certain number.
Informal:
* Five-lingual: This is a more informal way of saying "pentaglot."
* Fluent in five languages: This is a straightforward way of describing the person's ability.
Ultimately, the best way to describe someone who speaks five languages depends on the context and your personal preference.