verb: nod off is what happens when your eyes and brain disobey you, and begin entering hibernation mode even though you know you should be up and awake. Nodding off happens most often when you sit in a comfortable seat in the back of the room during boring classes with droning old professors. Some people are gifted with the screensaver mode, which they can turn on to cover up the fact that they have nodded off
John Doe: "hey, don't nod-off now! you're in the first row for God's sake!"