Definition of "rod"
rod
/ɹɒd/
noun
plural rods
(US) engineer's or surveyor's rod commonly is eight or ten feet long and often designed to extend higher. In former times a surveyor's rod often was a single wooden pole or composed of multiple sectioned and socketed pieces, and besides serving as a sighting target was used to measure distance on the ground horizontally, hence for convenience was of one rod or pole in length, that is, 5+1⁄2 yards.
(mathematics) A Cuisenaire rod.