The term "nud-mod" is a combination of two words: "nud" and "modified". In the context of adult content, it usually refers to scenes where actors are either partially or completely naked but with some kind of modification on their bodies. This could be anything from temporary tattoos, body paint, makeup, prosthetic additions, or even a modified appearance due to a physical condition like vitiligo. Essentially, "nud-mod" is a tag used for scenes that involve nudity with an altered or modified aspect of the actors' bodies.