/ Dictionary / Index S sp. gr.: Meaning and Definition of Find definitions for: sp. gr. Pronunciation: [key] specific gravity. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. SPF sphaeristerium Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language