Grease Shingle
The shit smear left on the back of the toilet seat. Commonly caused by explosive diarrhea or incorrectly positioning your asshole on the back of the toilet.
"At last year's company holiday party I got so drunk I accidentally left a grease shingle."

"I took this girl home from the bar last night, when I woke up she was gone...but the skank left me a grease shingle as a parting gift." #greaseshingle

Donald Trump's hair looks like a grease shingle.

Yo bro, quit being such a grease shingle.