/ Dictionary / Index D Department of Defense: Meaning and Definition of Find definitions for: Depart'ment of Defense' Pronunciation: [key] the department of the U.S. federal government charged with ensuring that the military capacity of the U.S. is adequate to safeguard the national security. Abbr.: DOD Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Department of Commerce Department of Education Related Content Daily Word Quiz: effervescent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language