devilish

Adjective

• playful in an appealingly bold way
  • a roguish grin
    

• 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
    

Adverb

• in a playfully devilish manner
  • the socialists are further handicapped if they believe that capitalists are not only wicked but also devilishly clever
    

Related words

• Synonyms: 
  rascally , roguish , diabolic , diabolical , mephistophelian , mephistophelean , devilishly