'nog lip' is a phrase used to describe a potentially embarassing situation when a man takes a sip of eggnog at a christmas party and gets some on his upper lip, unbeknownest to him.
It can also refer to someone who has been given something resembling nog lip, such as a nice wide shot on the lip after a romantic entanglement.
This phrase first appeared on the Phil Hendrie show in early December, 2004.
"I was at the Christmas Party and didn't know that I had nog lip. Then Elton John asked me to dance."
"I gave my girlfriend nog lip and now she's dumped me."