An illegal tenant is typically someone who occupies a space without permission or proper documentation. There are several synonyms to describe such a person, such as a squatter, an unauthorized occupant, or an illicit occupier. Other terms that may be used include a trespasser or an interloper. These words suggest that the person is not entitled to occupy the space granted to them, whether it be a rented room, apartment, or commercial property. In some cases, an illegal tenant may also be referred to as an invader, loiterer, or an intruder. Regardless of the term used, an illegal tenant represents a significant legal issue and may require immediate legal action.