One of the pair of testes (also gonad or testicle) common to all male mammals. They are held in the scrotum. Along with the penis, the testes constitute the male reproductory organs.
Turkey neck, or a penoscrotal web, is where the skin is so tight that, when erect, some skin from the scrotum is pulled forward on the bottom or ventral side of the penis.
The front or lower surface of a body, limb, or object; opposed to dorsal. When discussing the penis, it refers to the bottom side of the penis, specificly the portion that touches the scrotum when flaccid.