n.tuft of small stiff feathers on the first digit of a bird's wing
同义词：alulaspurious wing
英汉双解大词典
bastard wing
1.
N（名词）
a tuft of feathers attached to the first digit of a bird, distinct from the wing feathers attached to the other digits and the ulna (鸟类的)小翼羽 (Also called alula)