1. Marked by deception
   - underhand, underhanded 
2. Marked by quiet and caution and secrecy; taking pains to avoid being observed
   - furtive, sneak, stealthy, surreptitious

Derived forms: sneakier, sneakiest

See also: bent [Brit], concealed, corrupt, crooked, sneak, sneakily, sneakiness

Encyclopedia: Sneaky

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