wag

Short definition from Wiktionary

Verb

1. 1
   To swing from side to side, as an animal's tail, or someone's head to express disagreement or disbelief.
2. 2
   To play truant from school.
3. 3
   To go; to proceed; to move; to progress.
4. 4
   To move continually, especially in gossip; said of the tongue.
5. 5
   To leave; to depart.
6. 6
   Of the tail (lower order of the batting lineup): to score more runs than expected.

Noun

1. 1
   An oscillating movement.
2. 2
   A witty person.
3. 3
   A wife or girlfriend of a sports star or other celebrity, originally and especially of an association football player.
4. 4
   A wild-assed guess; a rough estimate.