/ Dictionary / Index P pentobarbital: Meaning and Definition of Find definitions for: pen•to•bar•bi•tal Pronunciation: (pen"tu-bär'bi-tôl", -tal"), [key] — n. Pharm. a barbiturate, CHNO, used as a hypnotic and as a sedative. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: pentobarbital (Thesaurus) pentlandite pentode 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