a. 1. Resembling, characteristic of, or pertaining to, the devil; diabolical; wicked in the extreme. “Devilish wickedness.” Sir P. Sidney. [ 1913 Webster ]
This wisdom descendeth not from above, but is earthly, sensual, devilish. James iii. 15. [ 1913 Webster ]
(adj) showing the cunning or ingenuity or wickedness typical of a devil, Syn. diabolic, mephistophelean, mephistophelian, diabolical, Example:devilish schemes; the cold calculation and diabolic art of some statesmen; the diabolical expression on his face; a mephistophelian glint in his eye
(adv) in a playfully devilish manner, Syn. devilish, Example:the socialists are further handicapped if they believe that capitalists are not only wicked but also devilishly clever