\Per`i*to*ne"um\, n. [L. peritoneum, peritonaeum, Gr.
?, ?, fr. ? to stretch all around or over; ? around + ? 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 {periton[ae]um}.]