| secret(adjective, sensitive, intimate, private, hidden) |
| back entrance(noun, expression, idiom) |
| stealthy(adjective, clandestine, underground, undisclosed) |
| arcane(adjective, obscure, deep, intimate, secret) |
| backstairs(adjective, close, sensitive, secret, restricted) |
| clandestine(adjective, underground, undisclosed) |
| confidential(adjective, intimate, secret, private, clandestine) |
| covert(adjective, clandestine, underground, undisclosed) |
| cryptic(adjective, close, obscure, unknown, inside) |
| furtive(adjective, close, obscure, unknown, clandestine) |
| surreptitious(adjective, clandestine, underground, undisclosed) |
| undercover(adjective, clandestine, underground, undisclosed) |
| underground(adjective, obscure, unknown, clandestine, undisclosed) |
| underhanded(adjective, clandestine, underground, undisclosed) |
| back door(expression, idiom) |
| backstage |
| camouflaged(close, obscure, unknown, clandestine, underground) |
| classified(obscure, sensitive, intimate, secret, private) |
| cloak-and-dagger(obscure, unknown, clandestine, underground, undisclosed) |
| close(obscure, intimate, private, unknown, inside) |