OXYUR′IS (Neo-Lat., from Gk. ὀξύς, oxys, sharp, quick, acid + ὀυρά, oura, tail). A nematode worm belonging to the Ascaridæ, characterized by a fusiform shape and a rounded oval aperture. The variety vermicularis is the thread-worm or maw-worm found in the sigmoid flexure and in the rectum of human beings. In horses this worm is called the bot. The male is ⅛ inch, the female nearly ½ inch in length. See Anthelmintic.