half-moon \half"-moon`\ -m=oon`, n.
   1. the moon at the quarters, when half its disk appears
      illuminated.
      1913 webster

   2. the shape of a half-moon; a crescent.
      1913 webster

            see how in warlike muster they appear,
            in rhombs, and wedges, and half-moons, and wings.
                                                  --milton.
      1913 webster

   3. fort. an outwork composed of two faces, forming a
      salient angle whose gorge resembles a half-moon; -- now
      called a ravelin.
      1913 webster

   4. zool. a marine, sparoid, food fish of california
      caesiosoma californiense. the body is ovate,
      blackish above, blue or gray below. called also
      medialuna.
      1913 webster
see also:
ravelin caesiosoma californiense medialuna 

ravelin \rave"lin\ ra^v"li^n; 277, n. f.; cf. sp.
   rebellin, it. revellino, rivellino; perhaps fr. l. re- again
   + vallum wall. fort.
   a detached work with two embankments which make a salient
   angle. it is raised before the curtain on the counterscarp of
   the place. formerly called demilune and half-moon.
   1913 webster
see also:
demilune half-moon 

half-moon
     n 1: the crescent-shaped area at the base of the human fingernail
          syn: lunula, lunule
     2: the time at which the moon is at first or last quarter when
        half its face is illuminated
see also:
lunula lunule