/ Dictionary / Index S SI units: Meaning and Definition of Find definitions for: SI units. Pronunciation: [key] See under Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sitzmark Siva Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language