| unassuming(quiet, plain, imperceptible, discreet, inconspicuous) |
| unconspicuous(adjective, inconspicuous) |
| under assumed name |
| under cover(expression, underhanded, privy) |
| underground(obscure, secret, unknown, clandestine, undisclosed) |
| undisclosed(obscure, unknown, clandestine, underground, unrevealed) |
| unenlightened(obscure, unknown, clandestine, underground, undisclosed) |
| unfrequented(obscure, unknown, clandestine, underground, undisclosed) |
| unintelligible(obscure, unknown, clandestine, underground, undisclosed) |
| unknown(obscure, clandestine, underground, undisclosed, unrevealed) |
| unpublished(obscure, unknown, clandestine, underground, undisclosed) |
| unsuspected(secret, hidden, clandestine, underground, underhanded) |
| whitewashed |
| QT(secret, hidden, clandestine, underground, underhanded) |
| abstruse(obscure, unknown, clandestine, underground, undisclosed) |
| ambiguous(obscure, unknown, clandestine, underground, undisclosed) |
| ambushed |
| arcane(obscure, unknown, clandestine, underground, undisclosed) |
| barely discernible(expression, idiom) |
| bound |