The Collaborative International Dictionary of English v.0.48:

Wet \Wet\ (w[e^]t), a. [Compar. Wetter; superl. Wettest.]
   [OE. wet, weet, AS. w[=ae]t; akin to OFries. w[=e]t, Icel.
   v[=a]tr, Sw. v[*a]t, Dan. vaad, and E. water. [root]137. See
   Water.]
   [1913 Webster]
   1. Containing, or consisting of, water or other liquid;
      moist; soaked with a liquid; having water or other liquid
      upon the surface; as, wet land; a wet cloth; a wet table.
      "Wet cheeks." --Shak.
      [1913 Webster]

   2. Very damp; rainy; as, wet weather; a wet season. "Wet
      October's torrent flood." --Milton.
      [1913 Webster]

   3. (Chem.) Employing, or done by means of, water or some
      other liquid; as, the wet extraction of copper, in
      distinction from dry extraction in which dry heat or
      fusion is employed.
      [1913 Webster]

   4. Refreshed with liquor; drunk. [Slang] --Prior.
      [1913 Webster]

   Wet blanket, Wet dock, etc. See under Blanket, Dock,
      etc.

   Wet goods, intoxicating liquors. [Slang]
      [1913 Webster]

   Syn: Nasty; humid; damp; moist. See Nasty.
        [1913 Webster]

WordNet (r) 3.0 (2006):

wet blanket
    n 1: someone who spoils the pleasure of others [syn:
         spoilsport, killjoy, wet blanket, party pooper]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "wet blanket":
   Foamite, acid, automatic sprinkler, bore, buttonholer, carbon tet,
   carbon tetrachloride, carbon-dioxide foam, chill, cold water,
   crashing bore, crepehanger, damp, damper, deck gun, deluge set,
   determent, deterrent, discouragement, drag, drip, dryasdust, dusty,
   extinguisher, fire apparatus, fire engine, fire hose, fire hydrant,
   fireplug, flat tire, foam, foam extinguisher, frightful bore,
   grouch, headache, hook-and-ladder, humdrum, killjoy, ladder pipe,
   malcontent, nuisance, pessimist, pest, pill, proser, pumper,
   snorkel, soda, sourpuss, spoilsport, sprinkler, sprinkler head,
   sprinkler system, super-pumper, twaddler, water, water cannon