Source : Webster's Revised Unabridged Dictionary (1913)

Rumen \Ru"men\, n. [L. rumen, - inis, the throat.]
   1. (Anat.) The first stomach of ruminants; the paunch; the
      fardingbag. See Illust. below.

Source : WordNet®

rumen
     n : the first compartment of the stomach of a ruminant; here
         food is collected and returned to the mouth as cud for
         chewing [syn: {first stomach}]
     [also: {rumina} (pl)]