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
see also:
rood perch pole black rod rods and cones