The Collaborative International Dictionary of English v.0.48:

dehumidify \de*hu*mid"i*fy\ v. t.
   to remove the moisture from (air or another gas); to reduce
   the humidity of; as, The air conditioner dehumidifies the air
   in the summer.

   Syn: make less humid.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

dehumidify
    v 1: make less humid; "The air conditioner dehumidifies the air
         in the summer" [ant: humidify, moisturise,
         moisturize]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "dehumidify":
   air-dry, anhydrate, bake, blot, brush, burn, cure, dehydrate,
   desiccate, drain, dry, evaporate, exsiccate, fire, insolate, kiln,
   mummify, parch, rub, scorch, sear, shrivel, smoke, soak up, sponge,
   sun, sun-dry, swab, torrefy, towel, weazen, wipe, wither, wizen