The Collaborative International Dictionary of English v.0.48:

Moisture \Mois"ture\, n. [Cf. OF. moistour, F. moiteur.]
   1. A moderate degree of wetness. --Bacon.
      [1913 Webster]

   2. That which moistens or makes damp or wet; exuding fluid;
      liquid in small quantity.
      [1913 Webster]

            All my body's moisture
            Scarce serves to quench my furnace-burning heat.
                                                  --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

moisture
    n 1: wetness caused by water; "drops of wet gleamed on the
         window" [syn: moisture, wet]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "moisture":
   Scotch mist, blood rain, chylifaction, chylification, drizzle,
   evening mist, fall, flow, fluency, fluidity, fluidness, flurry,
   flux, fluxility, fluxion, gout of rain, juiciness, lactation,
   lactescence, liquefaction, liquidness, milkiness, mist, misty rain,
   mizzle, patter, pitter-patter, precipitation, rain, raindrop,
   rainfall, rainwater, rheuminess, sappiness, serosity,
   sheet of rain, shower, splatter, sprinkle, succulence, suppuration,
   unfrozen hydrometeor, wateriness, wet