To ejaculate. Typically on a part of the body. For example, on the face (i.e. facial), in the mouth, on the breasts, on the legs or buttocks. Some fetishes even shown 'cumshots' on leather boots. Cumshots typically refer to a male ejaculating on a female but also include ejaculation on another male, inanimate objects, animals, or simply into the air (the cum falls where it may). The cumshot is very popular in pornography perhaps due to its explicit sexual nature which excites many.
Silvia Saint took a beautiful cumshot all over her face and tits.