/ Dictionary / Index S signa: Meaning and Definition of Find definitions for: sig•na Pronunciation: (sig'nu), [key] (used imperatively, in prescriptions) mark; write; label. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sign signable Related Content Daily Word Quiz: hedonist Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language