The Collaborative International Dictionary of English v.0.48:

Lock \Lock\, n. [AS. loc inclosure, an inclosed place, the
   fastening of a door, fr. l[=u]can to lock, fasten; akin to
   OS. l[=u]kan (in comp.), D. luiken, OHG. l[=u]hhan, Icel.
   l[=u]ka, Goth. l[=u]kan (in comp.); cf. Skr. ruj to break.
   Cf. Locket.]
   1. Anything that fastens; specifically, a fastening, as for a
      door, a lid, a trunk, a drawer, and the like, in which a
      bolt is moved by a key so as to hold or to release the
      thing fastened.
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   2. A fastening together or interlacing; a closing of one
      thing upon another; a state of being fixed or immovable.
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            Albemarle Street closed by a lock of carriages. --De
                                                  Quincey.
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   3. A place from which egress is prevented, as by a lock.
      --Dryden.
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   4. The barrier or works which confine the water of a stream
      or canal.
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   5. An inclosure in a canal with gates at each end, used in
      raising or lowering boats as they pass from one level to
      another; -- called also lift lock.
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   6. That part or apparatus of a firearm by which the charge is
      exploded; as, a matchlock, flintlock, percussion lock,
      etc.
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   7. A device for keeping a wheel from turning.
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   8. A grapple in wrestling. --Milton.
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   Detector lock, a lock containing a contrivance for showing
      whether it as has been tampered with.

   Lock bay (Canals), the body of water in a lock chamber.

   Lock chamber, the inclosed space between the gates of a
      canal lock.

   Lock nut. See Check nut, under Check.

   Lock plate, a plate to which the mechanism of a gunlock is
      attached.

   Lock rail (Arch.), in ordinary paneled doors, the rail
      nearest the lock.

   Lock rand (Masonry), a range of bond stone. --Knight.

   Mortise lock, a door lock inserted in a mortise.

   Rim lock, a lock fastened to the face of a door, thus
      differing from a mortise lock.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lock chamber
    n 1: enclosure consisting of a section of canal that can be
         closed to control the water level; used to raise or lower
         vessels that pass through it [syn: lock, lock chamber]