sneaky in WordNet English dictionary

1. marked by quiet and caution and secrecy; taking pains to avoid being observed
   "a furtive manner"; "a sneak attack"; "stealthy footsteps"; "a surreptitious glance at his watch"
   furtive  sneak  sneaky  stealthy  surreptitious 
   
2. marked by deception
   "achieved success in business only by underhand methods"
   sneaky  underhand  underhanded