| strong-minded(adjective, determined, fixed, stubborn) |
| sturdy(adjective, strong, hard, tough, firm) |
| tight(adjective, rigid) |
| uncaring(adjective, cold, indifferent, unyielding) |
| uncooperative(adjective, mean, hard, tough, persistent) |
| undeviating(adjective, strong, flat, harsh, certain) |
| unemotional(adjective, mean, hard, harsh, cold) |
| ungovernable(adjective, persistent, obstinate, insistent, dogged) |
| unhesitating |
| unmanageable(adjective, tough, firm, unreasonable, grim) |
| unmovable(adjective, firm, intense, resolute, persistent) |
| unruly(adjective, persistent, obstinate, insistent, dogged) |
| unshaken(adjective, strong, flat, firm, cold) |
| unsparing(adjective, strong, hard, tough, sturdy) |
| unstirred(adjective, cold, indifferent, impassive, steadfast) |
| stand pat(expression, adjective, strong, secure, flat) |
| untouched(adjective, cold, indifferent, unyielding) |
| unvarying |
| adamantean |
| arbitrary(adjective, hard, severe, rough, harsh) |