The Collaborative International Dictionary of English v.0.48:

Lock \Lock\, v. t. [imp. & p. p. Locked; p. pr. & vb. n.
   Locking.]
   1. To fasten with a lock, or as with a lock; to make fast; to
      prevent free movement of; as, to lock a door, a carriage
      wheel, a river, etc.
      [1913 Webster]

   2. To prevent ingress or access to, or exit from, by
      fastening the lock or locks of; -- often with up; as, to
      lock or lock up, a house, jail, room, trunk. etc.
      [1913 Webster]

   3. To fasten in or out, or to make secure by means of, or as
      with, locks; to confine, or to shut in or out -- often
      with up; as, to lock one's self in a room; to lock up the
      prisoners; to lock up one's silver; to lock intruders out
      of the house; to lock money into a vault; to lock a child
      in one's arms; to lock a secret in one's breast.
      [1913 Webster]

   4. To link together; to clasp closely; as, to lock arms. "
      Lock hand in hand." --Shak.
      [1913 Webster]

   5. (Canals) To furnish with locks; also, to raise or lower (a
      boat) in a lock.
      [1913 Webster]

   6. (Fencing) To seize, as the sword arm of an antagonist, by
      turning the left arm around it, to disarm him.
      [1913 Webster]

WordNet (r) 3.0 (2006):

locking
    n 1: the act of locking something up to protect it [syn:
         locking, lockup]