The Collaborative International Dictionary of English v.0.48:

desalinate \desalinate\ v. t.
   to remove the salt from, especially from water; as, it is
   necessary to desalinate sea water to make it fit to drink.

   Note: several processes are in comon use for desalinating sea
         water. Distillation is effective, but expensive.
         Reverse osmosis is more economical.

   Syn: desalt, desalinize.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

desalinate
    v 1: remove salt from; "desalinate water" [syn: desalinate,
         desalt, desalinize, desalinise] [ant: salinate]