Pronunciation: (fis'choo-lu),[key] —n., —pl.-las, -laePronunciation: (-lē").[key] 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 (fis'tulous with'ers), 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.