The Collaborative International Dictionary of English v.0.48:

Nut \Nut\ (n[u^]t), n. [OE. nute, note, AS. hnutu; akin to D.
   noot, G. nuss, OHG. nuz, Icel. hnot, Sw. n["o]t, Dan.
   n["o]d.]
   [1913 Webster]
   1. (Bot.) The fruit of certain trees and shrubs (as of the
      almond, walnut, hickory, beech, filbert, etc.), consisting
      of a hard and indehiscent shell inclosing a kernel.
      [1913 Webster]

   2. A perforated block (usually a small piece of metal),
      provided with an internal or female screw thread, used on
      a bolt, or screw, for tightening or holding something, or
      for transmitting motion. See Illust. of 1st Bolt.
      [1913 Webster]

   3. The tumbler of a gunlock. --Knight.
      [1913 Webster]

   4. (Naut.) A projection on each side of the shank of an
      anchor, to secure the stock in place.
      [1913 Webster]

   5. pl. Testicles. [vulgar slang]
      [PJC]

   Check nut, Jam nut, Lock nut, a nut which is screwed up
      tightly against another nut on the same bolt or screw, in
      order to prevent accidental unscrewing of the first nut.


   Nut buoy. See under Buoy.

   Nut coal, screened coal of a size smaller than stove coal
      and larger than pea coal; -- called also chestnut coal.


   Nut crab (Zool.), any leucosoid crab of the genus Ebalia
      as, Ebalia tuberosa of Europe.

   Nut grass (Bot.), See nut grass in the vocabulary.

   Nut lock, a device, as a metal plate bent up at the
      corners, to prevent a nut from becoming unscrewed, as by
      jarring.

   Nut pine. (Bot.) See under Pine.

   Nut rush (Bot.), a genus of cyperaceous plants (Scleria)
      having a hard bony achene. Several species are found in
      the United States and many more in tropical regions.

   Nut tree, a tree that bears nuts.

   Nut weevil (Zool.), any species of weevils of the genus
      Balaninus and other allied genera, which in the larval
      state live in nuts.
      [1913 Webster]

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.
      [1913 Webster]

   2. A fastening together or interlacing; a closing of one
      thing upon another; a state of being fixed or immovable.
      [1913 Webster]

            Albemarle Street closed by a lock of carriages. --De
                                                  Quincey.
      [1913 Webster]

   3. A place from which egress is prevented, as by a lock.
      --Dryden.
      [1913 Webster]

   4. The barrier or works which confine the water of a stream
      or canal.
      [1913 Webster]

   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.
      [1913 Webster]

   6. That part or apparatus of a firearm by which the charge is
      exploded; as, a matchlock, flintlock, percussion lock,
      etc.
      [1913 Webster]

   7. A device for keeping a wheel from turning.
      [1913 Webster]

   8. A grapple in wrestling. --Milton.
      [1913 Webster]

   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]

The Collaborative International Dictionary of English v.0.48:

locknut \locknut\, lock nut \lock nut\n.
   a supplementary nut that is screwed down on a primary nut to
   prevent it from loosening; a check nut.
   [WordNet 1.5]