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.

&fist; Each crescent is made of polyhedral cells which under some circumstances are supposed to give rise to new salivary cells.