The Collaborative International Dictionary of English v.0.48:

Intestine \In*tes"tine\, n.; pl. Intestines. [L. intestinum:
   cf. F. intestin. See Intestine, a.]
   [1913 Webster]
   1. (Anat.) That part of the alimentary canal between the
      stomach and the anus. See Illust. of Digestive apparatus.
      [1913 Webster]

   2. pl. The bowels; entrails; viscera.
      [1913 Webster]

   Large intestine (Human Anat. & Med.), the lower portion of
      the bowel, terminating at the anus. It is adapted for the
      retention of fecal matter, being shorter, broader, and
      less convoluted than the small intestine; it consists of
      three parts, the c[ae]cum, colon, and rectum.

   Small intestine (Human Anat. & Med.), the upper portion of
      the bowel, in which the process of digestion is
      practically completed. It is narrow and contorted, and
      consists of three parts, the duodenum, jejunum, and ileum.
      [1913 Webster]

WordNet (r) 3.0 (2006):

small intestine
    n 1: the longest part of the alimentary canal; where digestion
         is completed