| unobservable(adjective, invisible, latent) |
| unseeable |
| anonymous(adjective, concealed) |
| censored(verb, adjective, concealed) |
| clandestine(adjective, secret, hidden, underground, undisclosed) |
| dissembled(verb, close, secret, hidden, clandestine) |
| enshrouded(verb, adjective, concealed) |
| hush-hush(adjective, secret, hidden, clandestine, concealed) |
| incog(obscure, secret, unknown, hidden, underhanded) |
| masquerading(adjective, obscure, unknown, disguised, masked) |
| shrouded(obscure, secret, hidden, clandestine, underhanded) |
| stealthy(adjective, secret, hidden, clandestine, underground) |
| unnoticeable(adjective, quiet, plain, imperceptible, discreet) |
| unobtrusive(adjective, quiet, plain, imperceptible, discreet) |
| unperceived |
| unrevealed(adjective, obscure, unknown, clandestine, underground) |
| unseen(obscure, secret, unknown, hidden, covered) |
| backdoor(close, obscure, unknown, clandestine, underground) |
| backstairs(close, clandestine, underground, undisclosed, furtive) |
| bearded |