Source : Webster's Revised Unabridged Dictionary (1913)

Demilune \Dem"i*lune`\, n. [F. demi- lune.]
   1. (Fort.) A work constructed beyond the main ditch of a
      fortress, and in front of the curtain between two
      bastions, intended to defend the curtain; a ravelin. See
      {Ravelin}.

   2. (Physiol.) A crescentic mass of granular protoplasm
      present in the salivary glands.

   Note: Each crescent is made of polyhedral cells which under
         some circumstances are supposed to give rise to new
         salivary cells.