prepuce

The equivalent of the foreskin for male humans, the prepuce is a fold of skin and mucous membrane that forms a protective sheath around the penis when it is retracted. It typically has a much darker color and thicker skin than the penis itself.

While it is most prominent on horses, almost all male mammals have them, including dogs, in which case it is covered with fur rather than thick skin.

When the penis is retracted, also use sheathed penis.

Not to be confused with penis sheath, which is a type of clothing to cover the penis.