The act of wagging; a shake; as, a wag of the head.
source: Webster 1913
verb
move from side to side
The happy dog wagged his tail.
source: WordNet 3.0
To move one way and the other with quick turns; to shake to and fro; to move vibratingly; to cause to vibrate, as a part of the body; as, to wag the head.
source: Webster 1913
To move one way and the other; to be shaken to and fro; to vibrate.