Pediculous is a medical term that refers to an infestation of lice on the body. There are several synonyms for pediculous, including phthiriasis, pediculosis, and lousy. The term phthiriasis is derived from the Greek word phthir, which means louse, and is commonly used to describe an infestation of pubic lice. Pediculosis is a term used to describe infestations of both head lice and body lice, and is often used interchangeably with pediculous. Lousy is a colloquial term for an infestation of lice, and is often used to describe a person or situation that is unpleasant or undesirable.