The Collaborative International Dictionary of English v.0.48:

Rectrix \Rec"trix\ (-tr?ks), n.; pl. Rectrices (-tr?"s?z).
   [L., fem. of rector.]
   1. A governess; a rectoress.
      [1913 Webster]

   2. (Zool.) One of the quill feathers of the tail of a bird.
      [1913 Webster]