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).
(a) An instrument of punishment or correction;
He that spareth his rod hateth his son. --Prov.
(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.
2. A measure of length containing sixteen and a half feet; --
called also perch, and pole.
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.