The most popular interpretation seems to be somewhat conspicuously missing, unless it was, uhm, already deleted. I shall proceed irregardless.
The moment in a porn movie in which the male ejaculation is visible. Can also be a still shot of said moment in the case of printed pornography. This usually involves the man cumming on the woman's face (facial), breasts, stomach, or, in the case of doggystyle or other back-to-front sexual position, on her ass or back. Note that however tempting it is to refer to the ejaculation itself as the shot, it is generally believed that the camera shot is closer to the original meaning.
Also known as: cum shot