(1):
(n.) 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.
(2):
(n.) A reed; a pipe.
(3):
(n.) A pipe for convejing water.