The Collaborative International Dictionary of English v.0.48:

Canoness \Can"on*ess\, n. [Cf. LL. canonissa.]
   A woman who holds a canonry in a conventual chapter.
   [1913 Webster]

   Regular canoness, one bound by the vow of poverty, and
      observing a strict rule of life.

   Secular canoness, one allowed to hold private property, and
      bound only by vows of chastity and obedience so long as
      she chose to remain in the chapter.
      [1913 Webster] canonic