/ Dictionary / Index Q Q clearance: Meaning and Definition of Find definitions for: Q clearance Pronunciation: [key] (in the Nuclear Regulatory Commission) the highest level of security clearance, permitting access to secret information, documents, etc., relating to nuclear research. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Q-Celtic q.d. Related Content Daily Word Quiz: candor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language