wagtail

n any of various types of small bird with a long tail that moves constantly up and down when the bird is standing or walking （体小, 尾长而不停上下摆动）.

wafer-thin, waffle, waffle-iron, waft, wag, wage, wage freeze, wage-claim, wage-earner, wager, wages, waggish, waggishly, waggishness, waggle, waggon, wagon, wagon (Brit also waggon), wagon-lit, wagoner (Brit also waggoner), waif, wail, wainscot, wainscoted, wainscoting, waist, waist-deep, waist-high, waistband, waistcoat, waisted, waistline, wait, wait at table, wait for, wait on, wait up for, waiter, waiting room, waiting-list,