(Noun)Feces residue around the butthole that remains after a insufficeint whiping.
(Noun)When when you lick the crust off of someones rectum.
"Yo my girl gave me a rusty asshole."
"Yo son that kids gotta real rusty asshole."
"Yo, I ran outta fuckin whipes, now I gotta rusty asshole."
"Hey, my girl wants me to give her a rusty asshole tonight, I dont know if I want to though."