| privately(adverb, clandestine, underground, secretly, slyly) |
| spy(adjective, secret, warning, hidden, covert) |
| backstairs(adjective, mysterious, private, reticent, taciturn) |
| occult(secret, unknown, hidden, underground, concealed) |
| privy |
| underhanded(dishonest, cunning, deceitful, secret, hidden) |
| buried(adjective, secret, unknown, hidden, concealed) |
| clouded(secret, unknown, hidden, underground, concealed) |
| furtively(adverb, clandestine, underground, secretly, slyly) |
| mysterious(adjective, quiet, secret, private, reticent) |
| obscure(adjective, secret, unknown, hidden, concealed) |
| skulking(adjective, secret, private, hidden, sneak) |
| sneaking(adjective, dishonest, cunning, deceitful, secret) |
| sneaky(adjective, quiet, dishonest, cunning, secret) |
| sub rosa(expression, adjective, idiom, show, secret) |
| underneath(adjective, secret, hidden, spy, covert) |
| disguised(adjective, obscure, secret, hidden, clandestine) |
| incognito(adjective, adverb, informal, secret, hidden) |
| lurking |
| mystic(adjective, secret, unknown, hidden, underground) |