Military slang: a very low-ply, government-issue sheet used in an open-bay barracks/dormitory setting hanging from the top bunk to give the bottom-bunk dweller an area of partial privacy from which to beat the meat or flick the bean, as the situation dictates.
Sergeant Major: what the fuck are all these beatsheets doing hanging up in my barracks, sergeant?! Take that shit down before the whole battalion goes blind god dammit!
(aka "the hype-min") One who keeps the beat while the DJ is busy doing the following: mixing, drinking, smoking, dancing, going buck, uncle buck, crazy buck, n*gga buck, etc. swag.
Dude: "WowDJ Staxxx this party is out of control, how do you manage to spin that shit so nice doe?"
DJ Staxxx: "I wouldn't be able to do it without my beatkeeper Pauly D, he's the swag, and you best belee dat"