The Collaborative International Dictionary of English v.0.48:

Damascene \Dam"as*cene\ (d[a^]m"as*s[=e]n), n.
   A kind of plum, now called damson. See Damson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Damask \Dam"ask\, a.
   1. Pertaining to, or originating at, the city of Damascus;
      resembling the products or manufactures of Damascus.
      [1913 Webster]

   2. Having the color of the damask rose.
      [1913 Webster]

            But let concealment, like a worm i' the bud,
            Feed on her damask cheek.             --Shak.
      [1913 Webster]

   Damask color, a deep rose-color like that of the damask
      rose.

   Damask plum, a small dark-colored plum, generally called
      damson.

   Damask rose (Bot.), a large, pink, hardy, and very fragrant
      variety of rose (Rosa damascena) from Damascus. "Damask
      roses have not been known in England above one hundred
      years." --Bacon.

   Damask steel, or Damascus steel, steel of the kind
      originally made at Damascus, famous for its hardness, and
      its beautiful texture, ornamented with waving lines;
      especially, that which is inlaid with damaskeening; --
      formerly much valued for sword blades, from its great
      flexibility and tenacity.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Damson \Dam"son\ (d[a^]m"z'n), n. [OE. damasin the Damascus
   plum, fr. L. Damascenus. See Damascene.]
   A small oval plum of a blue color, the fruit of a variety of
   the Prunus domestica; -- called also damask plum.
   [1913 Webster]

WordNet (r) 3.0 (2006):

damson
    n 1: dark purple plum of the damson tree [syn: damson, damson
         plum]