| bullheaded(adjective, strong, hard, tough, severe) |
| inconvincible(adjective, determined, resolute, uncompromising, unshakeable) |
| pertinacious(adjective, determined, resolute, uncompromising, unshakeable) |
| perverse(adjective, determined, resolute, uncompromising, unshakeable) |
| powerful(adjective, strength) |
| rugged(adjective, set, strong, hard, tough) |
| self-opinionated(adjective, determined, resolute, uncompromising, unshakeable) |
| self-willed(adjective, determined, resolute, uncompromising, unshakeable) |
| solid(adjective, set, strong, hard, severe) |
| stout(adjective, strength) |
| wilful(adjective, determined, resolute, uncompromising, unshakeable) |
| willful(adjective, determined, resolute, uncompromising, unshakeable) |
| carbon |
| indurate(adjective, set, firm, determined, stiff) |
| intractable(hard, tough, firm, unreasonable, grim) |
| robust(adjective, strong, hard, strength, tough) |
| steady |
| unshakeable(adjective, determined, resolute, uncompromising) |
| C |
| dense(adjective, set, strong, hard, tough) |