Definition of wagtail :
Any one of many species of Old World singing birds belonging to Motacilla and several allied genera of the family Motacillidae. They have the habit of constantly jerking their long tails up and down, whence the name.
- Within reach from the window the swallows have their nests, and the sparrows their holes, on the right hand; within reach on the left hand, among the ivy, the water- wagtail has built her nest year after year. - "Wild Life in a Southern County", Richard Jefferies.
- And the water- wagtail, pushed forward by no gentle hand, appeared within the doorway. - "The Complete Historical Romances of Georg Ebers", Georg Ebers.
- When red- starts shake their tails they move them horizontally, as dogs do when they fawn: the tail of a wagtail, when in motion, bobs up and down like that of a jaded horse. - "The-Natural-History-of-Selborne", White, Gilbert.