Out has many dictionary definitions, such as away from inside or away from the middle. See wiktionary:out .
People are said to be out after having revealed that they are gay ( homosexual). More accurately, these people are in the process of coming out. See coming out of the closet. The phrase is also used for the revelation of other secrets, especially "skeletons".
Out is a gay-interest fashion magazine. See Out Magazine.
Out can also mean in or entering a state of unconsciousness.
In baseball, an out is recorded on a play which retires the batter or a base runner. See out (baseball).
This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.