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.
- Of or relating to a lower world of the dead.
- Of or relating to hell: infernal punishments; infernal powers.
- Fiendish; diabolical: infernal instruments of war.
- Abominable; awful: the infernal racket of the jackhammers.