chicken sleeping 

When you fall asleep in an upright position with your head dangling, most commonly in a car or airplane. The motion makes your head bob up and down like a chicken pecking. In rare cases, you could be fighting falling asleep in class and a moving vehicle is not necessary. Chances of chicken sleeping are increased by 70% after a wake and bake session or accounting class.

I was sitting behind her in class and thought she was paying attention. But then I walked by and saw that she was just chicken sleeping.

chicken sleeping by LIFOtheparty April 13, 2017