- having the qualities of a devil; devilish; fiendish; outrageously wicked: a diabolic plot.
- pertaining to or actuated by a devil.
- of, relating to, or proceeding from the devil; satanic
- befitting a devil; extremely cruel or wicked; fiendish
- very difficult or unpleasant
late 14c., from Old French diabolique (13c.), from Late Latin diabolicus, from Ecclesiastical Greek diabolikos “devilish,” from diabolos (see devil (n.)).