The American Heritage® Dictionary of the English Language, 4th Edition
n. The first division of the stomach of a ruminant animal, in which most food collects immediately after being swallowed and from which it is later returned to the mouth as cud for thorough chewing. Also called paunch.
the GNU version of the Collaborative International Dictionary of English
n. The first stomach of ruminants; the paunch; the fardingbag. See Illust. below.
n. The cud of a ruminant.
The Century Dictionary and Cyclopedia
n. The cud of a ruminant.
n. The paunch or first stomach of a ruminant; the largest of the four compartments of the ruminant stomach.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the first compartment of the stomach of a ruminant; here food is collected and returned to the mouth as cud for chewing
Word Usage
"Unlike converting methane from cow shit into electricity, a method that requires expensive gear, this method generates electricity as the microorganisms in rumen fluid break down the complex carbohydrates in roughage."