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1.
The wagging of the index finger of your dominant hand in a very stern and disapproving manner. This is done to show your disapproval of the (usually idiotic) actions of another. Note that the wagging must be done so slowly as to make it a very awkward situation.

Usually accompanied by the Look of Judgement
Mr. English Teacher: What are you doing on the floor?

Student: My cell phone fell out of my pocket...

Mr. English Teacher: *Gives the Stern Finger of Disapproval* Naughty.
by Colonel Duke Lacrosse December 03, 2011