The Collaborative International Dictionary of English v.0.48:

Dematerialize \De`ma*te"ri*al*ize\, v. t.
   To deprive of material or physical qualities or
   characteristics.
   [1913 Webster]

         Dematerializing matter by stripping it of everything
         which . . . has distinguished matter.    --Milman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dematerialize
    v 1: become immaterial; disappear [syn: dematerialize,
         dematerialise] [ant: happen, materialise,
         materialize]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "dematerialize":
   attenuate, be consumed, be gone, cease, cease to be,
   cease to exist, depart, die, die away, die out, disappear,
   disembody, disincarnate, dispel, disperse, dissipate, dissolve,
   do a fade-out, dwindle, enervate, erode, etherealize, evanesce,
   evaporate, exit, fade, fade away, fade out, flee, fly, go, go away,
   hide, idealize, immaterialize, insubstantialize, leave no trace,
   leave the scene, melt, melt away, pass, pass away, pass out,
   perish, rarefy, retire from sight, sap, sink, sink away, spiritize,
   spiritualize, subtilize, suffer an eclipse, unsubstantialize,
   vanish, vanish from sight, waste, waste away, weaken, wear away