| stubborn(adjective, characteristic, quality, strong, firm) |
| persistent(adjective, strong, tough, flat, firm) |
| firm(noun, adjective, clear, strong, sound) |
| determined(adjective, clear, strong, tough, severe) |
| resolute(adjective, clear, strong, tough, severe) |
| dogged(adjective, strong, tough, firm, resist) |
| obstinate(adjective, strong, firm, intense, resist) |
| pertinacious(adjective, strong, tough, firm, difficult) |
| unyielding(adjective, clear, strong, sound, tough) |
| steadfast(adjective, clear, strong, secure, tough) |
| inflexible(adjective, strong, determined, resolute, obstinate) |
| courageous(adjective, firm, determined, vigorous, bold) |
| persevering(adjective, strong, tough, flat, firm) |
| tough(adjective, strong, firm, determined, resolute) |
| obdurate(adjective, strong, determined, resolute, obstinate) |
| adamant(adjective, strong, determined, resolute, persistent) |
| set(adjective, strong, secure, flat, firm) |
| staunch(adjective, clear, strong, sound, tough) |
| unwavering(adjective, strong, flat, firm, intense) |
| relentless(adjective, strong, tough, firm, determined) |