\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.