| secret(adjective, sensitive, dishonest, cunning, deceitful) |
| secretive(adjective, dishonest, cunning, deceitful, reserved) |
| secretly |
| shrouded(obscure, unknown, unknowing, clandestine, underground) |
| silent(reserved, mysterious, private, reticent, taciturn) |
| sly(dishonest, cunning, deceitful, secret, private) |
| slyly(clandestine, quietly, secretly, personally, privately) |
| sneaking(dishonest, cunning, deceitful, private, hidden) |
| sneaky(dishonest, cunning, deceitful, secret, private) |
| stealthily(clandestine, quietly, secretly, personally, privately) |
| stealthy(dishonest, cunning, deceitful, secret, private) |
| sub-rosa(adjective, sensitive, dishonest, cunning, deceitful) |
| sub rosa(expression, clandestine, quietly, personally, privately) |
| surreptitious(adjective, dishonest, cunning, deceitful, secret) |
| surreptitiously(clandestine, quietly, secretly, personally, privately) |
| tight-lipped(reserved, mysterious, private, reticent, taciturn) |
| treacherous(dishonest, cunning, deceitful, fickle, untrustworthy) |
| two-timing(dishonest, cunning, deceitful, fickle, untrustworthy) |
| uncommunicative(adjective, shy, reserved, mysterious, private) |
| under-the-table(sensitive, secret, private, hidden, unknowing) |