/ Dictionary / Index S surd: Meaning and Definition of Find definitions for: surd Pronunciation: (sûrd), [key] — adj. voiceless (opposed to sonant). (of a quantity) not capable of being expressed in rational numbers; irrational. —n. a voiceless consonant (opposed to sonant). a surd quantity. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: surd (Thesaurus) surculose sure Related Content Daily Word Quiz: endear Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language