1. Alula definition is - a specialized structure of the upper leading edge of a bird's wing that consists of a tuft of short, stiff flight feathers attached to the movable first wing digit corresponding to the thumb and that facilitates flight, landing, and maneuverability at slow speeds : bastard wing

2. The Alula / ˈæljʊlə /, or bastard wing, (plural Alulae) is a small projection on the anterior edge of the wing of modern birds and a few non-avian dinosaurs. The word is Latin and means "winglet"; it is the diminutive of ala, meaning "wing".