ˈrümə̇n noun
( plural rumi·na -mənə ; or rumens )
Etymology: New Latin, from Latin, gullet — more at ruminate
: the large first compartment of the stomach of a ruminant from which food is regurgitated for rumination and in which cellulose is broken down by the action of bacterial and protozoan symbionts : paunch ; broadly : the first three compartments of the ruminant stomach — distinguished from abomasum ; compare omasum , reticulum