- any of numerous small passerine birds (family Motacillidae) mostly native to Europe, characterized by long wing feathers and a very long tail that wags up and down
- ☆ any of various similar birds, as an American waterthrush
See wagtail in American Heritage Dictionary 4
Any of various chiefly Old World birds of the family Motacillidae, having a slender body with a long tail that constantly wags.
Learn more about wagtail