Definitions for omasumoʊˈmeɪ səm
Random House Webster's College Dictionary
the third stomach of a ruminant, between the reticulum and the abomasum.
Origin of omasum:
1700–10; < NL; L omāsum ox's tripe
psalterium, omasum, third stomach(noun)
the third compartment of the stomach of a ruminant
The third part of the stomach of a ruminant.
Origin: From omasum
U.S. National Library of Medicine
The third stomach of ruminants, situated on the right side of the abdomen at a higher level than the fourth stomach and between this latter and the second stomach, with both of which it communicates. From its inner surface project large numbers of leaves or folia, each of which possesses roughened surfaces. In the center of each folium is a band of muscle fibers which produces a rasping movement of the leaf when it contracts. One leaf rubs against those on either side of it, and large particles of food material are ground down between the rough surfaces, preparatory to further digestion in the succeeding parts of the alimentary canal. (Black's Veterinary Dictionary, 17th ed)