| adamant(obstinate, stubborn, unbending) |
| adamantine(obstinate, stubborn, unbending) |
| determined(obstinate, stubborn, unbending) |
| dogged(obstinate, stubborn, unbending) |
| dyed-in-the-wool(obstinate, stubborn, unbending) |
| firm(obstinate, stubborn, unbending) |
| fixed(obstinate, stubborn, unbending) |
| hard(obstinate, stubborn, unbending) |
| hard-and-fast(obstinate, stubborn, unbending) |
| hard and fast(expression, adjective, idiom, inflexible, unbending) |
| hardened inflexible(expression, inflexible, unbending) |
| hardheaded(adjective, inflexible, unbending) |
| hidebound(adjective, inflexible, strict, obstinate, stubborn) |
| immovable(obstinate, stubborn, unbending) |
| immutable(obstinate, stubborn, unbending) |
| implacable(obstinate, stubborn, unbending) |
| indomitable(obstinate, stubborn, unbending) |
| inexorable(obstinate, stubborn, unbending) |
| inflexible(adjective, set, strict, obstinate, stubborn) |
| intractable(obstinate, stubborn, unbending) |