The act of putting cocaine (usually a significant amount) into your partners anus, then having them fart causing the cocaine to go up into the air. As they fart, it should go into your nose, or wait until they fart into the air causing a dust cloud, then snort it like that.
"Man, Jennifer and I went out last night"
"You guysdo it?"
"And we did coke on the rim!"
A dim rim is when you take a fat shit. Just a mean nasty raunchy shit that is sure to leave your asshole absolutely blackened with shit. Then someone eats your ass before you wipe. They eat your dimmed rim. They give you a dim rim.
Riding the Rim: To take a shit in such a way that all of the feces land on the rim of the toilet with none landing either in the toilet or on the floor. If one then lowers the toliet seat down on top of the feces on the rim, you call it "Making A Smore".