underhanded (adj.)

• artful
• backstairs
• calculating
• clandestine
• collusive
• conscienceless
• corrupt
• corrupted
• covert
• crafty
• criminal
• crooked
• cunning
• dark
• deceitful
• devious
• dishonest
• dishonorable
• doubtful
• dubious
• duplicitous
• evasive
• false
• feline
• felonious
• fishy
• fraudulent
• furtive
• guileful
• hole-and-corner
• hugger-mugger
• ill-gotten
• immoral
• indirect
• insidious
• privy
• questionable
• quiet
• rotten
• scheming
• shady
• shameless
• sharp
• shifty
• sinister
• slippery
• sly
• sneaking
• sneaky
• stealthy
• surreptitious
• suspicious
• treacherous
• tricky
• two-faced
• unconscientious
• unconscionable
• under-the-counter
• under-the-table
• undercover
• underground
• underhand
• undermanned
• understaffed
• unethical
• unobtrusive
• unprincipled
• unsavory
• unscrupulous
• wily