/ Dictionary / Index P phenobarbital: Meaning and Definition of Find definitions for: phe•no•bar•bi•tal Pronunciation: (fē"nō-bär'bi-tôl", -tal", -nu-), [key] — n. Pharm. a white, crystalline powder, CHNO, used as a sedative, a hypnotic, and as an antispasmodic in epilepsy. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: phenobarbital (Thesaurus) pheno- phenocopy Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language