The Collaborative International Dictionary of English v.0.48:
Omentum \O*men"tum\, n.; pl. Omenta. [L.] (Anat.)
A free fold of the peritoneum, or one serving to connect
viscera, support blood vessels, etc.; an epiploon.
Note: The great, or gastrocolic, omentum forms, in most
mammals, a great sac, which is attached to the stomach
and transverse colon, is loaded with fat, and covers
more or less of the intestines; the caul. The lesser,
or gastrohepatic, omentum connects the stomach and
liver and contains the hepatic vessels. The
gastrosplenic omentum, or ligament, connects the
stomach and spleen.
WordNet (r) 3.0 (2006):
n 1: a fold of peritoneum supporting the viscera