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.
Usually the final bit of a porn movie where the guy with a huge cock pulls out of the actress's pussy and shoots his jizz all over her face. Often said actress will hold her mouth wide open and stare up at the guy imploringly, and frequently then make a big show of rolling it around in her mouth, blowing bubbles, etc.
I downloaded a collection of cum shots off Kazaa this afternoon.