Synonyms for Devilish (same or very similar meaning)
WordNet sense 1 (playful in an appealingly bold way):
rascally, roguishWordNet sense 2 (full of fun and high spirits):
playfulWordNet sense 3 (showing the cunning or ingenuity or wickedness typical of a devil):
diabolic, diabolical, mephistophelean, mephistophelianWordNet sense 4 (morally bad or wrong):
evilWordNet sense 5 (in a playfully devilish manner):
devilishlyFrom the ODE community, based on WordNetadd/edit