/ Dictionary / Index R rotational quantum number: Meaning and Definition of Find definitions for: rota'tional quan'tum num"ber Pronunciation: [key] — Physics. Physics. the quantum number that distinguishes the angular momentum states associated with the rotational motion of a molecule. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. rotational molding rotation axis Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language