ETYM Latin.
An abnormal passage leading from a suppurating cavity to the body surface; SYN. sinus.
Pipe; very deep ulcer; pipelike passage from ulcer to surface or between hollow organs.
In medicine, an abnormal pathway developing between adjoining organs or tissues, or leading to the exterior of the body. A fistula developing between the bowel and the bladder, for instance, may give rise to urinary-tract infection by intestinal organisms.
Long narrow passage or duct.