/fis"choo leuh/ , n. , pl. fistulas, fistulae /-lee'/ .
1. Pathol. a narrow passage or duct formed by disease or injury, as one leading from an abscess to a free surface, or from one cavity to another.
2. Surg. an opening made into a hollow organ, as the bladder or eyeball, for drainage.
3. Vet. Pathol. any of various suppurative inflammations, as in the withers of a horse (fistulous withers) , characterized by the formation of passages or sinuses through the tissues and to the surface of the skin.
4. Obs. a pipe, as a flute.
[ 1350-1400; ME ]