/ Dictionary / Index S semper fidelis*: Meaning and Definition of Find definitions for: sem•per fi•de•lis Pronunciation: (sem'per fi-dā'lis Eng. sem'p&schwar fi-dā'lis, -dē'-), [key] — Latin. Latin. always faithful: motto of the U.S. Marine Corps. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. semper fi semper idem* Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language