| tough(adjective, hard, sharp, firm, fixed) |
| tough-nut(adjective, hard, tough, difficult, wild) |
| tough nut(expression, adjective, fixed, impassive, inflexible) |
| unalterable(adjective, severe, fixed, stiff, impassive) |
| unbending(adjective, tough, severe, cruel, pitiless) |
| uncooperative(adjective, tough, difficult, wild, awkward) |
| undisciplined(adjective, tough, difficult, wild, awkward) |
| unflappable(adjective, firm, determined, usual, regular) |
| unflexible(adjective, tough, firm, distant, rigid) |
| ungovernable(adjective, tough, difficult, wild, determined) |
| unmanageable(adjective, tough, difficult, wild, awkward) |
| unpliable(adjective, tough, difficult, wild, awkward) |
| unruly(adjective, tough, difficult, wild, determined) |
| unswayable(adjective, tough, firm, fixed, distant) |
| uptight(adjective, tough, firm, fixed, distant) |
| usual(adjective, firm, determined, regular, planned) |
| wayward(adjective, tough, difficult, wild, awkward) |
| well-set(adjective, firm, determined, usual, regular) |
| willful(adjective, tough, difficult, wild, determined) |
| bedfast(adjective, restrained, captive, confined, enclosed) |