<p><strong>noun</strong></p><ul><li>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.</li><li>an opening made into a hollow organ, as the bladder or eyeball, for drainage.</li><li>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.</li><li>an object, as a theatrical prop, constructed so that it breaks or falls apart easily, especially upon impact.</li></ul>