The Collaborative International Dictionary of English v.0.48:

Rail \Rail\, n. [Akin to LG. & Sw. regel bar, bolt, G. riegel a
   rail, bar, or bolt, OHG. rigil, rigel, bar, bolt, and
   possibly to E. row a line.]
   1. A bar of timber or metal, usually horizontal or nearly so,
      extending from one post or support to another, as in
      fences, balustrades, staircases, etc.
      [1913 Webster]

   2. (Arch.) A horizontal piece in a frame or paneling. See
      Illust. of Style.
      [1913 Webster]

   3. (Railroad) A bar of steel or iron, forming part of the
      track on which the wheels roll. It is usually shaped with
      reference to vertical strength, and is held in place by
      chairs, splices, etc.
      [1913 Webster]

   4. (Naut.)
      (a) The stout, narrow plank that forms the top of the
          bulwarks.
      (b) The light, fencelike structures of wood or metal at
          the break of the deck, and elsewhere where such
          protection is needed.
          [1913 Webster]

   5. A railroad as a means of transportation; as, to go by
      rail; a place not accesible by rail.
      [Webster 1913 Suppl.]

   6. a railing.
      [PJC]

   Rail fence. See under Fence.

   Rail guard.
      (a) A device attached to the front of a locomotive on each
          side for clearing the rail of obstructions.
      (b) A guard rail. See under Guard.

   Rail joint (Railroad), a splice connecting the adjacent
      ends of rails, in distinction from a chair, which is
      merely a seat. The two devices are sometimes united. Among
      several hundred varieties, the fish joint is standard. See
      Fish joint, under Fish.

   Rail train (Iron & Steel Manuf.), a train of rolls in a
      rolling mill, for making rails for railroads from blooms
      or billets.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Fence \Fence\ (f[e^]ns), n. [Abbrev. from defence.]
   1. That which fends off attack or danger; a defense; a
      protection; a cover; security; shield.
      [1913 Webster]

            Let us be backed with God and with the seas,
            Which he hath given for fence impregnable. --Shak.
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            A fence betwixt us and the victor's wrath.
                                                  --Addison.
      [1913 Webster]

   2. An inclosure about a field or other space, or about any
      object; especially, an inclosing structure of wood, iron,
      or other material, intended to prevent intrusion from
      without or straying from within.
      [1913 Webster]

            Leaps o'er the fence with ease into the fold.
                                                  --Milton.
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   Note: In England a hedge, ditch, or wall, as well as a
         structure of boards, palings, or rails, is called a
         fence.
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   3. (Locks) A projection on the bolt, which passes through the
      tumbler gates in locking and unlocking.
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   4. Self-defense by the use of the sword; the art and practice
      of fencing and sword play; hence, skill in debate and
      repartee. See Fencing.
      [1913 Webster]

            Enjoy your dear wit, and gay rhetoric,
            That hath so well been taught her dazzing fence.
                                                  --Milton.
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            Of dauntless courage and consummate skill in fence.
                                                  --Macaulay.
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   5. A receiver of stolen goods, or a place where they are
      received. [Slang] --Mayhew.
      [1913 Webster]

   Fence month (Forest Law), the month in which female deer
      are fawning, when hunting is prohibited. --Bullokar.

   Fence roof, a covering for defense. "They fitted their
      shields close to one another in manner of a fence roof."
      --Holland.

   Fence time, the breeding time of fish or game, when they
      should not be killed.

   Rail fence, a fence made of rails, sometimes supported by
      posts.

   Ring fence, a fence which encircles a large area, or a
      whole estate, within one inclosure.

   Worm fence, a zigzag fence composed of rails crossing one
      another at their ends; -- called also snake fence, or
      Virginia rail fence.

   To be on the fence, to be undecided or uncommitted in
      respect to two opposing parties or policies. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

rail fence
    n 1: a fence (usually made of split logs laid across each other
         at an angle)