/ Dictionary / Index P posthaste: Meaning and Definition of Find definitions for: post•haste Pronunciation: (pōst'hāst'), [key] — adv. with the greatest possible speed or promptness: to come to a friend's aid posthaste. —n. great haste. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. postgraduate postheat Related Content Daily Word Quiz: lyceum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language