| cautious(sneaky, covert, secretive) |
| circumspect(sneaky, covert, secretive) |
| clandestinely(clandestine, secretly, slyly, underhandedly, surreptitiously) |
| cloak and dagger(expression, idiom, hidden, fraudulent) |
| confidential(secret, hidden, spy, clandestine, underground) |
| cover(obscure, ulterior) |
| creep(secret, hidden, spy, covert) |
| crooked(dishonest, cunning, deceitful, sneaky, underhanded) |
| deceitful(dishonest, sneaky, underhanded) |
| deceptive(dishonest, cunning, deceitful, sneaky, underhanded) |
| deep(clandestine, underground, undisclosed) |
| devious(dishonest, cunning, deceitful, sneaky, underhanded) |
| dirty-dealing(dishonest, cunning, deceitful, sneaky, underhanded) |
| dirty dealing(expression, dishonest, deceitful, underhanded) |
| dishonest(cunning, deceitful, sneaky, underhanded, underhand) |
| dishonorable(dishonest, cunning, deceitful, sneaky, underhanded) |
| dissembled(secret, hidden, clandestine, underground, undisclosed) |
| dissimulated(clandestine, underground, undisclosed) |
| double-crossing(dishonest, cunning, deceitful, sneaky, underhanded) |
| duplicitous(dishonest, cunning, deceitful, sneaky, underhanded) |