The practice of reforming a portion of a memory foam mattress into a shape resembling an orifice in order to fornicate with same. A true topgrading is done to the mattress of another in order to exact some form of revenge (see, eg. "top shelf" or "upper decker" et al.)
"Garret's topgrading session was interrupted by a mirror crashing down from Trisha and Brad's wall. He nonetheless reached climax and decided this had made it all the more satisfying."
The mid-coital act of assessing a woman's performance, while she is engaged in the cowgirl position.
"I was getting close to busting a nut, but she got pissed off when I topgraded her, and she stormed out."
"My pregnant wife always cries, when I start topgrading her, yet she wants me to be more open with my feelings - and what just started to happen there, didn't FEEL as good as when my girlfriend does it."