When snot is snorted into the throat and hocked into the mouth, then spit out. This is usually a thicker mucous than normal spit, and goes further. It also has a much sweeter and delightful taste than normal spit. Lungies are especially deadly when they are hocked in conjunction with a bloody nose. It's choice to wait around 10 minutes before bleeding subsides before doing this act.
I made my girl put a blindfold on and spit a lungie on her upper lip, she thought it was cum until she ate it all up and realized it was nothin but my snot.