The word "wag" usually refers to the side-to-side movement of a dog's tail, which usually means that the dog is happy, excited, or friendly. Full definition
There are always plenty of tail wags at the Portland Saturday Market. (wagwalking.com)
Every Tuesday evening, our van (full of wagging tails) heads down the road. (okcpetsmagazine.com)
If your dog exhibits all the qualities necessary for successful dog agility training, then you will be granted lots of joy and happy tail wagging in the ring. (puppy-training-solutions.com)