Cats wag their tails to send messages to both humans and other animals. The positioning of the tail as well as the position of the ears and the cat's facial expression are all clues as to what the cat's tail wag or wave means.
The tail flick is one of the common cat tail wags. The cat holds the tail lower and then extends it quickly while flicking it back and forth. This is a sign of offensive aggression. This can be seen often when a cat is brought to the veterinarian's office. The cat flicks the tail on the exam room table to let the veterinarian know that it is not happy to be there.
Another cat tail wag is called the vertical hold. This happens when the cat takes its tail and holds it straight up. Sometimes there will be a bit of back and forth. This means that the cat is happy and in a playful mood; however, if the tail is being held upright but is curved slightly inward then the cat does not interact and is in a defensive position.
The arched tail is a cat tail wag where the cat has pinned his or her ears back and has an arched back along with an arched or erect tail. This cat is letting everyone know that he or she is ready for the defensive or the offensive. The cat is ready to react to anything.