Peritoneum

n. serous membrane lining the abdominal cavity (Anatomy)

In higher vertebrates, the peritoneum is the serous membrane that forms the lining of the abdominal cavity - it covers most of the intra-abdominal organs. It is composed of a layer of mesothelium supported by a thin layer of connective tissue.The peritoneum both supports the abdominal organs and serves as a conduit for their blood and lymph vessels and nerves.
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(n.)
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.
  

The membrane that lines the abdominal cavity and covers most of the abdominal organs. (From the Greek peri- meaning around + tonos meaning a stretching = a stretching around).

[PAIR-ih-toe-NEE-um]
The tissue that lines the abdominal wall and covers most of the organs in the abdomen.