Antonyms of lock:
disengage, unlock, withdraw, dark horse, long shot.
Examples of usage:
  1. " Clear the lock," Rip ordered.
    "Rip Foster in Ride the Gray Planet", Harold Leland Goodwin.
  2. " Beudant," said Marion, " lock that door quick!"
    "First Person Paramount", Ambrose Pratt.
  3. Dale entered, turning the key in the lock behind her.
    "The Bat", Avery Hopwood Mary Roberts Rinehart.