The Collaborative International Dictionary of English v.0.48:

Mesocolon \Mes`o*co"lon\, n. [NL., fr. Gr. meso`kwlon; me`sos
   middle + kw^lon the colon: cf. F. m['e]soc[^o]lon.] (Anat.)
   The fold of peritoneum, or mesentery, attached to the colon.
   -- Mes`o*col"ic, a.
   [1913 Webster]