The Collaborative International Dictionary of English v.0.48:

Mesentery \Mes"en*ter*y\ (?; 277), n. [Gr. mesente`rion, me`sos
   + 'e`nteron intestine: cf. F. m['e]sent[`e]re.]
   [1913 Webster]
   1. (Anat.) The membranes, or one of the membranes (consisting
      of a fold of the peritoneum and inclosed tissues), which
      connect the intestines and their appendages with the
      dorsal wall of the abdominal cavity. The mesentery proper
      is connected with the jejunum and ilium, the other
      mesenteries being called mesocaecum, mesocolon,
      mesorectum, etc.
      [1913 Webster]

   2. (Zool.) One of the vertical muscular radiating partitions
      which divide the body cavity of Anthozoa into chambers.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mesentery
    n 1: a double layer of peritoneum that attaches to the back wall
         of the abdominal cavity and supports the small intestines