: any of the quill feathers of a bird's tail that are important in controlling flight direction — see bird illustration
Did You Know?
Although "rectrix" (from the Latin word rectrix, the feminine of rector, meaning "one that directs") has been an English word since the late 18th century, it has clung to its Latin plural rectrices. This is not terribly unusual for a technical term like "rectrix." (Note also "cilium," whose more common plural "cilia" refers especially to the hairlike extensions on the exterior of some cells.) "Rectrix" has another meaning wholly unrelated to birds. It's also used (albeit rarely) to refer to a woman who rules or governs.