/ Dictionary / Index D diradical: Meaning and Definition of Find definitions for: di•rad•i•cal Pronunciation: (dī-rad'i-kul), [key] — n. Chem. an atom or molecule having two unpaired electrons. Also calledCf. free radical. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Dirac delta function Dirae Related Content Daily Word Quiz: digression Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language