/ Dictionary / Index S SDI: Meaning and Definition of Find definitions for: SDI Pronunciation: [key] Strategic Defense Initiative: technical name of Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. 'sdeath S. Doc. Related Content Daily Word Quiz: procrastinate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language