in·fer·nal 
(ĭn-fûrnəl)
(ĭn-fûrnəl)adj.
1.
a. Of or relating to a lower world of the dead.
b. Of or relating to hell: infernal punishments; infernal powers.
2. Fiendish; diabolical: infernal instruments of war.
3. Abominable; awful: the infernal racket of the jackhammers.
[Middle English, from Old French, from Late Latin īnfernālis, from īnfernus, hell, from Latin, lower, underground; see dher- in the Appendix of Indo-European roots.]
in·fernal·ly adv.