| behind the curtain(expression, idiom) |
| close(obscure, dark, secret, unknown, hidden) |
| clouded(obscure, dark, secret, unknown, hidden) |
| covered(obscure, secret, unknown, hidden, concealed) |
| deep(obscure, unknown, clandestine, underground, undisclosed) |
| disregarded(ignored, undiscovered, overlooked, unobserved) |
| eclipsed(obscure, dark, secret, unknown, hidden) |
| esoteric(adjective, obscure, dark, secret, unknown) |
| faint |
| glossed over(expression, ignored, undiscovered, overlooked, unobserved) |
| hermetic(obscure, dark, secret, unknown, hidden) |
| hermetical(obscure, dark, secret, unknown, hidden) |
| hush-hush(secret, hidden, clandestine, underground, undisclosed) |
| imperceivable(adjective, obscure, dark, secret, unknown) |
| in the background(expression, idiom, latency implication) |
| in the dark(expression, idiom, obscure, dark, unknown) |
| incognito(secret, hidden, clandestine, underground, undisclosed) |
| indiscoverable |
| indistinct |
| insensible |