Well, it could mean a variety of things to a variety of people, but generally, the “bottom” is the guy who is the receptive partner in anal sex. Although it could be a label for someone who is more sub within sex.
So the guy who’s underneath (or on top if you’re doing the cowboy) is known as the “bottom”. The giver is known as the “Top”. Not everybody likes the terms “top” or “bottom” for some being a bottom is seen as less than, more subservient or more effeminate, but some, like Big Brother US star Ragan Fox, have empowered the word and meaning by calling themselves, “power bottoms”.
Otherwise, you could go with giver and givee, catcher and pitcher or just their names… (no labels!)
Apparently, there’s quite a bit of stigma attached to being a bottom. A survey found sixty per cent of readers thought that there was or weren’t sure if there was a stigma attached to bottoming or being the receiving partner during penetrative sex.
Only 40 per cent said no there wasn’t a stigma.