/ Dictionary / Index S Seconal: Meaning and Definition of Find definitions for: Sec•o•nal Pronunciation: (sek'u-nôl", -nal", -nl), [key] — Pharm., Trademark. Pharm.,Trademark. a brand of secobarbital. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: seconal (Thesaurus) secobarbital second Related Content Daily Word Quiz: supercilious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language