sneaky as in marked by deception

• "achieved success in business only by underhand methods"

Synonyms

• underhandslyly and secretly; with the hand swung below shoulder level; with hand brought forward and up from below shoulder level; marked by deception
• underhandedmarked by deception; with hand brought forward and up from below shoulder level

sneaky as in 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"

Synonyms

• furtivemarked by quiet and caution and secrecy; secret and sly or sordid
• sneak(a)
• stealthymarked by quiet and caution and secrecy
• surreptitiousmarked by quiet and caution and secrecy; conducted with or marked by hidden aims or methods