semilunar valves

from The Collaborative International Dictionary of English v.0.48

Semilunar \Sem`i*lu"nar\, a.
   Shaped like a half moon.
   [1913 Webster]

   {Semilunar bone} (Anat.), a bone of the carpus; the lunar.
      See {Lunar}, n.

   {Semilunar valves}, or {Sigmoid valves} (Anat.), the valves
      at the beginning of the aorta and of the pulmonary artery
      which prevent the blood from flowing back into the
      ventricle.
      [1913 Webster]