| treasonous(fickle, untrustworthy, unprincipled, dirty-dealing) |
| trustless(fickle, untrustworthy, unprincipled) |
| unassured(fickle, untrustworthy, unprincipled) |
| unauthorized(adjective, secret, private, hidden, sneaky) |
| unconverted(fickle, untrustworthy, unprincipled, dirty-dealing) |
| under the table(expression, sensitive, sneaky, covert, recreant) |
| underground(adjective, secret, hidden, spy, clandestine) |
| underneath(adjective, secret, hidden, spy, covert) |
| undisclosed(clandestine, underground) |
| undutiful(fickle, untrustworthy, unprincipled, dirty-dealing) |
| unenlightened(clandestine, underground, undisclosed) |
| unfaithful(fickle, untrustworthy, unprincipled, dirty-dealing) |
| unfrequented(clandestine, underground, undisclosed) |
| unintelligible(clandestine, underground, undisclosed) |
| unknown(clandestine, underground, undisclosed) |
| unloyal(fickle, untrustworthy, unprincipled, dirty-dealing) |
| unpatriotic(fickle, untrustworthy, unprincipled, dirty-dealing) |
| unprincipled(fickle, untrustworthy, dirty-dealing) |
| unpublished(clandestine, underground, undisclosed) |
| unrevealed(clandestine, underground, undisclosed) |