The Collaborative International Dictionary of English v.0.48:

Tunicle \Tu"ni*cle\, n. [L. tunicula a little tunic, coat, or
   membrane, dim. of tunica a tunic: cf. OF. tunicle.]
   1. A slight natural covering; an integument.
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            The tunicles that make the ball or apple of the eye.
                                                  --Holland.
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   2. (R. C. Ch.) A short, close-fitting vestment worn by
      bishops under the dalmatic, and by subdeacons.
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