This is the term used to describe dried-up, crusty, and usually week-old semen that has been resting on a man's penis or scrotum for an extended period of time. From-Under Cheese comes from sloppy masturbation most of the time, but can also be a result of complete uncleanliness.
Bitch: OMG I'm soooo fuckkkin drunk...I wanna suck your fuckkkin dick...haha
Me: Ight bitch. Lick the From-Under Cheese off while you're at it.
Joe was beating off for 2 straight hours and had a load of From-Under Cheese under there.
Eminem (Crack a Bottle): Kiss my butt, lick From-Under Cheese from under my nuts.