Term used when someone walks unknowingly into an area where someone has just crop dusted with their mouth open. Leaving the person feeling as though they had just been stabbed in the face with someone's ass matter.
Bob wondered who open ass face shanked him in aisle 3 of the grocery store.
Bill thought farting in mary's cubicle would be a funny open ass face shank.
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).