What is a perv?

Answer 1

Perv (noun, slang)

The slang word "perv" is used colloquially for someone with an inappropriate sexual slant to their thoughts or actions. Adolescents use the term as an epithet against a peer who precociously applies sexual overtones to acts or conversation. (The term was famously adopted for a "dirty old man" character in the translated Naruto anime series.)

Perversion (source)

Perversion is a concept describing those types of human behavior that are a serious deviation from what is considered to be orthodox or normal. Although it can refer to varying forms of deviation, it is most often used to describe sexual behaviors that are seen by the majority as abnormal, repulsive or obsessive. Perversion differs from deviant behavior, since the latter refers to a recognized violation of social rules or norms. It is often considered derogatory and in psychological literature the term paraphilia is now used instead, though this term is controversial.