What does it mean to "unload" in gay porn?

What is unload?

Common slang term for when a male ejaculates, usually a large amount of semen.

Definition

Generally meaning the act of where a male will ejaculate, and that the amount of semen is a rather large amount.

Noteworthy: Popular term used in pornographic videos and sites, to indicate that large amounts of cum are shown, usually from multiple participants, rather than solo action.