peritoneum
peri.to.ne.um \.per-*t-*n-'e--*m\ \-'e--*mz\ \-'e--*\ n or peri.to.ne.ums or peri.to.nea [LL, fr. Gk peritonaion, neut. of peritonaios stretched around, fr.] pl peri- + tenein to stretch - more at THIN 1: the smooth transparent serous membrane that lines the cavity of the abdo men of a mammal and is reflected inward over the abdominal and pelvic viscera 2: PLEUROPERITONEUM