| adamant(adjective, strong, hard, tough, firm) |
| adamantine(adjective, strong, hard, tough, sturdy) |
| ardent(adjective, close, correct, firm, honest) |
| deep |
| deep-rooted |
| dyed-in-the-wool(adjective, close, strong, hard, tough) |
| enduring(adjective, close, correct, firm, honest) |
| entrenched |
| firm(adjective, close, strong, hard, tough) |
| flinty(adjective, strong, hard, tough, severe) |
| grim(adjective, strong, hard, tough, severe) |
| hot(vulgar, indecent, lewd) |
| immovable(adjective, strong, hard, tough, firm) |
| implacable(adjective, strong, hard, tough, severe) |
| inexorable(adjective, strong, hard, tough, severe) |
| loyal(adjective, close, correct, firm, honest) |
| relentless(adjective, strong, hard, tough, severe) |
| rigorous(adjective, strong, hard, tough, severe) |
| rooted |
| settled |