(a.) Like a traitor; involving treachery; violating allegiance or faith pledged; perfidious\ in private life; betraying a trust; faithless.

Machiavellian Punic ambidextrous artful calculating chancy chiseling collusive covinous crafty crooked cunning dangerous deceitful deceptive desultory dishonest disloyal double double-crossing double-dealing double-faced double-minded double-tongued doublehearted doubtful dubious duplicitous faithless FALSE false-principled falsehearted finagling fraudulent furtive guileful hairy hazardous indirect infirm insecure insidious insubstantial jeopardous misleading perfidious perilous precarious precariousness provisional recreant risky rocky scheming shaky sharp shifting shifty slippery sneaky surreptitious temporary tentative ticklish tottery traitorous trickish tricky two-faced uncertain undependable underhand underhanded unfaithful unfaithworthy unhealthy unloyal unpredictable unreliable unsafe unsolid unsound unstable unsteadfast unsteady unsubstantial unsure untrue untrustworthy wicked wily