Disturbingly provocative:
— An intriguing smile.

synonym: challenging.

Roget 702: cunning, crafty, artful; skillful etc. 698; subtle, feline, vulpine; cunning as a fox, cunning as a serpent; deep, deep laid; profound; designing, contriving; intriguing etc. v.; strategic, diplomatic, politic, Machiavelian, timeserving^†; artificial; tricky, tricksy^†; wily, sly, slim, insidious, stealthy; underhand etc. (hidden) 528; subdolous^†; deceitful etc. 545; slippery as an eel, evasive etc. 623; crooked; arch, pawky^†, shrewd, acute; sharp, sharp as a tack, sharp as a needle^†; canny, astute, leery, knowing, up to snuff, too clever by half, not to be caught with chaff.    tactful, diplomatic, politic; polite etc. 894.    ... show more

Capable of arousing interest or curiosity.