/ Dictionary / Index P portentous: Meaning and Definition of Find definitions for: por•ten•tous Pronunciation: (pôr-ten'tus, pōr-), [key] — adj. of the nature of a portent; momentous. ominously significant or indicative: a portentous defeat. marvelous; amazing; prodigious. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: portentous (Thesaurus) portent porter Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language