LUNG bu ter noun -term used for the discharge that comes out of one's lungs after a severe coughing spell while one has a respiratory infection. the color and texture are quite similar to butter.
Dude 1: "Holy Shit Man. That's one hellofa cough you have. You gonna be ok?
Dude 2: "Yea man, the shit I'm hackin' up looks just like lung butter."
Dude 1: "Fuck man. That's nasty shit."