Polyhistor is a term used to describe a person who has extensive knowledge in many different fields. However, there are several synonyms that can be used to describe such a person. One such synonym is "polymath," which refers to someone who has expertise in multiple fields such as literature, math, science, and art. Another synonym is "renaissance man/woman," which refers to someone who has a broad range of knowledge and skills. "Universal genius" is also a synonym for polyhistor and refers to someone who excels in many areas of expertise. Additionally, "scholar" and "learned person" are synonyms that can be used to describe someone who has extensive knowledge in various fields.