OMASUM Meaning of OMASUM in English [ əʊ'meɪsəm ]■ noun ( plural omasa -sə ) Zoology the muscular third stomach of a ruminant animal, between the reticulum and the ab~.OriginC18: from L., lit. 'bullock's tripe'. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004