peritoneum

n. [ L. peritoneum, peritonaeum, Gr. &unr_;, &unr_;, fr. &unr_; to stretch all around or over; peri` around + &unr_; to stretch. ] (Anat.) The smooth serous membrane which lines the cavity of the abdomen, or the whole body cavity when there is no diaphragm, and, turning back, surrounds the viscera, forming a closed, or nearly closed, sac. [ Written also peritonæum. ] [ 1913 Webster ]