Longman Dictionary of Contemporary English - wag

~1 v 1 to shake your finger or head repeatedly, especially to show disapproval  (wag your finger)  ("You naughty girl!" Mom said, wagging her finger at me.) 2 if a dog wags its tail, it moves it repeatedly from one side to the other 3 tongues wag informal used to say that people are talking in a disapproving way about someone else's behaviour  (You'll have to stop visiting that woman - tongues are starting to wag.) ~2 n 1 C usually singular a wagging movement 2 old-fashioned someone who talks or does something in a clever and amusing way  (Some wag had drawn a face on the wall.)  (- see also chinwag, waggish)