"devilish" in the adjective sense
1. devilish, diabolic, diabolical, mephistophelian, mephistophelean
showing the cunning or ingenuity or wickedness typical of a devil
"the cold calculation and diabolic art of some statesmen"
"the diabolical expression on his face"
"a mephistophelian glint in his eye"
2. devilish, rascally, roguish
playful in an appealingly bold way
"a roguish grin"
"devilish" in the adverb sense
1. devilishly, devilish
in a playfully devilish manner
"the socialists are further handicapped if they believe that capitalists are not only wicked but also devilishly clever"
Source: WordNet® (An amazing lexical database of English)
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