| rigid(adjective, material, behavior, conviction, stiffness) |
| solid(adjective, material, conviction, stiffness) |
| inflexible(adjective, material, behavior, conviction, stiffness) |
| firm(adjective, material, behavior, conviction, stiffness) |
| stiff(adjective, material, conviction, stiffness) |
| fixed(adjective, conviction, stiffness) |
| adamant(adjective, material, behavior, conviction, stiffness) |
| hard(adjective, material, behavior, conviction, stiffness) |
| impliable(adjective, material, rare, conviction, stiffness) |
| intractable(adjective, material, behavior, conviction, stiffness) |
| unbending(adjective, material, behavior, conviction, stiffness) |
| unyielding(adjective, material, behavior, conviction, stiffness) |
| determined(adjective, behavior, conviction, stiffness) |
| hard-line(adjective, behavior, conviction, stiffness) |
| hard-nosed(adjective, behavior, conviction, stiffness) |
| headstrong(adjective, behavior, conviction, stiffness) |
| immalleable(adjective, material, conviction, stiffness) |
| implacable(adjective, behavior, conviction, stiffness) |
| inexorable(adjective, behavior, conviction, stiffness) |
| mulish(adjective, behavior, conviction, stiffness) |