- 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.
- an opening made into a hollow organ, as the bladder or eyeball, for drainage.
- 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.
- a pipe, as a flute.
- an abnormal opening between one hollow organ and another or between a hollow organ and the surface of the skin, caused by ulceration, congenital malformation, etc
- any musical wind instrument; a pipe
