The Collaborative International Dictionary of English v.0.48:

Rod \Rod\, n. [The same word as rood. See Rood.]
   1. A straight and slender stick; a wand; hence, any slender
      bar, as of wood or metal (applied to various purposes).
      Specifically:
      (a) An instrument of punishment or correction;
          figuratively, chastisement.
          [1913 Webster]

                He that spareth his rod hateth his son. --Prov.
                                                  xiii. 24.
          [1913 Webster]
      (b) A kind of sceptor, or badge of office; hence,
          figuratively, power; authority; tyranny; oppression.
          "The rod, and bird of peace." --Shak.
      (c) A support for a fishing line; a fish pole. --Gay.
      (d) (Mach. & Structure) A member used in tension, as for
          sustaining a suspended weight, or in tension and
          compression, as for transmitting reciprocating motion,
          etc.; a connecting bar.
      (e) An instrument for measuring.
          [1913 Webster]

   2. A measure of length containing sixteen and a half feet; --
      called also perch, and pole.
      [1913 Webster]

   Black rod. See in the Vocabulary.

   Rods and cones (Anat.), the elongated cells or elements of
      the sensory layer of the retina, some of which are
      cylindrical, others somewhat conical.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Black Rod \Black" Rod`\
   (a) the usher to the Chapter of the Garter, so called from
       the black rod which he carries. He is of the king's
       chamber, and also usher to the House of Lords. [Eng.]
   (b) An usher in the legislature of British colonies.
       --Cowell.
       [1913 Webster]

             Committed to the custody of the Black Rod.
                                                  --Macaulay.
       [1913 Webster]