- hellish; fiendish; diabolical: an infernal plot.
- extremely troublesome, annoying, etc.; outrageous: an infernal nuisance.
- of, inhabiting, or befitting hell.
- Classical Mythology. of or relating to the underworld.
- of or relating to an underworld of the dead
- deserving hell or befitting its occupants; diabolic; fiendish
- informal irritating; confounded
late 14c., in reference to the underworld, from Old French enfernal, infernal (12c.), from Late Latin infernalis “of the lower regions,” from infernus “hell” (Ambrose), literally “the lower (world),” noun use of Latin infernus “lower, lying beneath,” from infra “below” (see infra-). Meaning “devilish, hateful” is from early 15c. For the name of the place, or things which resemble it, the Italian form inferno has been used in English since 1834, from Dante. Related: Infernally.