A moment of great realization punctuated by a loud and often drawn out "Ohhhhhh". It is a phenominon experience by all but the incredibly dull or inattentive.
Math Teacher: "...and that is how you find a derivitive."
Student 1: Ohhhhhhhhhhhhh. Now i get it.
Student 2: I wish I could have an Ohment, i still dont get it.