To cup (not grab, cup) someones buttocks and yell, "Peaches!" If you successfully 'peach' the person, you yell "Got 'em!" If you slap someone instead of simply peaching, it does not count as a peach and therefore you did not complete the process of 'peaching'.
Dude, Jennifer was totally peaching all the guys at your party last week.
After an individual takes a very satisfying shit on the toilet, it is essential for them to wipe. If you begin walking after taking a shit and a few pieces of shit or "muddy water" fall or drip down your leg you are by defintion "peaching off crumbs."
O shit, look at that girl, she obviously did not finish wiping her ass, because she is peaching off crumbs!