abomasumEnglishOxford New American Dictionaryabomasum /ˌabəˈmāsəm, ˌæbəˈmeɪsəm / ▸ noun (plural abomasa /-sə/) Zoology the fourth stomach of a ruminant, which receives food from the omasum and passes it to the small intestine. – ORIGIN late 17th century: modern Latin, from ab- ‘away, from’ + omasum (see omasum).