The phase in that people enter when they drink a glass of milk. Can be easily identified because of the blank stare they give with wide eyes. Is a combination of the words moo
When someone is in the mook, there mind goes blank, they dont notice any of their surroundings, and all they can think about is drinking that glass o' milk.
The next time you eat dinner, watch someone drink some milk and youll see them enter the mook.