/ Dictionary / Index I infernal: Meaning and Definition of Find definitions for: in•fer•nal Pronunciation: (in-fûr'nl), [key] — adj. hellish; fiendish; diabolical: an infernal plot. extremely troublesome, annoying, etc.; outrageous: an infernal nuisance. of, inhabiting, or befitting hell. of or pertaining to the underworld. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: infernal (Thesaurus) inferior vena cava infernal machine Related Content Daily Word Quiz: spectral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language