sigmoidal

from WordNet (r) 3.0 (2006)

sigmoidal
    adj 1: of or relating to the sigmoid flexure in the large
           intestine [syn: {sigmoid}, {sigmoidal}]

from The Collaborative International Dictionary of English v.0.48

Sigmoid \Sig"moid\, Sigmoidal \Sig*moid"al\, a. [Gr. ???; ???
   sigma + e'i^dos form, likeness: cf. F. sigmo["i]de.]
   Curved in two directions, like the letter S, or the Greek
   [sigmat].
   [1913 Webster]

   {Sigmoid flexure} (Anat.), the last curve of the colon before
      it terminates in the rectum. See Illust. under
      {Digestive}.

   {Sigmoid valves}. (Anat.) See {Semilunar valves}, under
      {Semilunar}.
      [1913 Webster]