The Collaborative International Dictionary of English v.0.48:

nerve \nerve\ (n[~e]rv), n. [OE. nerfe, F. nerf, L. nervus, akin
   to Gr. ney^ron sinew, nerve; cf. neyra` string, bowstring;
   perh. akin to E. needle. Cf. Neuralgia.]
   1. (Anat.) One of the whitish and elastic bundles of fibers,
      with the accompanying tissues, which transmit nervous
      impulses between nerve centers and various parts of the
      animal body.
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   Note: An ordinary nerve is made up of several bundles of
         nerve fibers, each bundle inclosed in a special sheath
         (the perineurium) and all bound together in a
         connective tissue sheath and framework (the epineurium)
         containing blood vessels and lymphatics.
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   2. A sinew or a tendon. --Pope.
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   3. Physical force or steadiness; muscular power and control;
      constitutional vigor.
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            he led me on to mightiest deeds,
            Above the nerve of mortal arm.        --Milton.
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   4. Steadiness and firmness of mind; self-command in personal
      danger, or under suffering; unshaken courage and
      endurance; coolness; pluck; resolution.
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   5. Audacity; assurance. [Slang]
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   6. (Bot.) One of the principal fibrovascular bundles or ribs
      of a leaf, especially when these extend straight from the
      base or the midrib of the leaf.
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   7. (Zool.) One of the nervures, or veins, in the wings of
      insects.
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   Nerve cell (Anat.), a neuron, one of the nucleated cells
      with which nerve fibers are connected; a ganglion cell
      is one type of nerve cell.

   Nerve fiber (Anat.), one of the fibers of which nerves are
      made up. These fibers are either medullated or
      nonmedullated. In both kinds the essential part is the
      translucent threadlike axis cylinder which is continuous
      the whole length of the fiber.

   Nerve stretching (Med.), the operation of stretching a
      nerve in order to remedy diseases such as tetanus, which
      are supposed to be influenced by the condition of the
      nerve or its connections.
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WordNet (r) 3.0 (2006):

nerve fiber
    n 1: a threadlike extension of a nerve cell [syn: nerve fiber,
         nerve fibre]