Source : Webster's Revised Unabridged Dictionary (1913)

Unfreeze \Un*freeze"\, v. t. [1st pref. un- + freeze.]
   To thaw. [Obs.]

Source : WordNet®

unfreeze
     v 1: become or cause to become soft or liquid; "The sun melted
          the ice"; "the ice thawed"; "the ice cream melted"; "The
          heat melted the wax"; "The giant iceberg dissolved over
          the years during the global warming phase"; "dethaw the
          meat" [syn: {dissolve}, {thaw}, {unthaw}, {dethaw}, {melt}]
     2: make (assets) available; "release the holdings in the
        dictator's bank account" [syn: {unblock}, {free}, {release}]
        [ant: {freeze}, {freeze}]
     [also: {unfrozen}, {unfroze}]