The Collaborative International Dictionary of English v.0.48:

Fistula \Fis"tu*la\ (?; 135), n.; pl. Fistul[ae]. [L.]
   1. A reed; a pipe.
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   2. A pipe for convejing water. [Obs.] --Knight.
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   3. (Med.) A permanent abnormal opening into the soft parts
      with a constant discharge; a deep, narrow, chronic
      abscess; an abnormal opening between an internal cavity
      and another cavity or the surface; as, a salivary fistula;
      an anal fistula; a recto-vaginal fistula.
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   Incomplete fistula (Med.), a fistula open at one end only.
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