Real Dictionary

wag
verb: If you wag your finger, you shake it repeatedly and quickly from side to side, usually because you are annoyed with someone.
verb: If you wag your head, you move it from side to side, often because you are unhappy about a situation.
verb: When a dog wags its tail, it repeatedly waves its tail from side to side.

wag in American English
intransitive verb: to be moved from side to side or one way and the other, esp. rapidly and repeatedly, as the head or the tail
noun: the act of wagging
transitive verb: to move from side to side, forward and backward, or up and down, esp. rapidly and repeatedly

wag in American English 1
to cause (something fastened or held at one end) to move rapidly and repeatedly back and forth, from side to side, or up and down

wag in American English 2
a comical or humorous person; joker; wit

Wag in British English
abbreviation for: (West Africa) Gambia (international car registration)
noun: the wife or girlfriend of a famous sportsman

wag in British English 1
noun: the act or an instance of wagging
verb: to move or cause to move rapidly and repeatedly from side to side or up and down

wag in British English 2
noun: a humorous or jocular person; wit