say it: dahy-uh-BAH-li-kuhl
diabolical is an adjective meaning "showing the cunning or ingenuity or wickedness typical of a devil". It carries 2 recorded senses.
showing the cunning or ingenuity or wickedness typical of a devil
“devilish schemes”
“the cold calculation and diabolic art of some statesmen”
“the diabolical expression on his face”
“a mephistophelian glint in his eye”
extremely evil or cruel; expressive of cruelty or befitting hell
“something demonic in him--something that could be cruel”
“fires lit up a diabolic scene”
“diabolical sorcerers under the influence of devils”
“a fiendish despot”
“hellish torture”
“infernal instruments of war”
“satanic cruelty”
“unholy grimaces”
Definitions, synonyms and semantic relations for diabolical come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.