/ Dictionary / Index C control rod: Meaning and Definition of Find definitions for: control' rod" Pronunciation: [key] a neutron-absorbing material, as boron or cadmium, in the shape of a rod or other configuration, that can be moved into or out of the core of a nuclear reactor to regulate the rate of fission. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. control rocket control room Related Content Daily Word Quiz: languid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language