Source : Webster's Revised Unabridged Dictionary (1913)

Unlock \Un*lock"\, v. t. [Cf. AS. unl?can. See 1st {Un-}, and
   {Lock}, v. t.]
   1. To unfasten, as what is locked; as, to unlock a door or a
      chest.

   2. To open, in general; to lay open; to undo.

            Unlock your springs, and open all your shades.
                                                  --Pope.

            [Lord] unlock the spell of sin.       --J. H.
                                                  Newman.

Source : WordNet®

unlock
     v 1: open the lock of; "unlock the door" [ant: {lock}]
     2: set free or release
     3: become unlocked; "The door unlocked from the inside" [ant: {lock},
         {lock}]