Infernal1. (a.) Pertaining to hell; diabolical; as, infernal spirits, or conduct; suitable for hell, or to the character of the inhabitants of hell; hellish.
2. (a.) of or pertaining to or suitable for the lower regions, inhabited, according to the ancients, by the dead; pertaining to Pluto's realm of the dead, the Tartarus of the ancients.
3. (n.) An inhabitant of the infernal regions; also, the place itself.
Thesaurus Entries
Acherontic, Draconian, Hadean, Lethean, Mephistophelian, Plutonian, Plutonic, Stygian, Tartarean, absolute, animal, anthropophagous, atrocious, barbaric, barbarous, beastly, bestial, blamed, blasted, blessed, bloodthirsty, bloody, bloody-minded, brutal, brutalized, brute, brutish, cannibalistic, chthonian, chthonic, cimmerian, confounded, cruel, cruel-hearted, cursed, cussed, damnable, damned, demoniac, demoniacal, demonic, demonical, devilish, diabolic, diabolical, dire, downright, dreadful, evil, execrable, fell, feral, ferocious, fiendish, fiendlike, fierce, flagitious, ghoulish, heinous, hellborn, hellish, inhuman, inhumane, iniquitous, maleficent, malevolent, malicious, murderous, nether, out-and-out, outright, pandemoniac, pandemonic, plutonian, plutonic, purgatorial, ruthless, sadistic, sanguinary, sanguineous, satanic, savage, sharkish, sinister, slavering, straight-out, stygian, subhuman, sulfurous, thoroughgoing, truculent, unchristian, uncivilized, underworld, ungodly, unhuman, vicious, villainous, wicked, wolfish