Pĕr′-i-to-nē′um, n.

n. [Lat. peritonæum and peritonæum, Gr. περιτόναιον, περιτόναινον, from περιτείνειν, to stretch all round or over, from περί, around, and τείνειν, to stretch; Fr. péritoine, Sp. & It. peritoneo.] (Anat.) A thin, smooth, serous membrane, investing the whole internal surface of the abdomen, and more or less completely all the viscera contained in it, and of which it forms the surface.