Source : Webster's Revised Unabridged Dictionary (1913)

Moistener \Mois"ten*er\, n.
   One who, or that which, moistens. --Johnson.

Source : WordNet®

moistener
     n : a device that dampens or moistens something; "he used a
         dampener to moisten the shirts before he ironed them"
         [syn: {dampener}]