| still(adjective, certain, limited, definite, inflexible) |
| stipulated(adjective, certain, limited, definite, inflexible) |
| straight(adjective, even, rigid, inflexible, reliable) |
| sure(adjective, certain, limited, definite, inflexible) |
| systematic(adjective, even, rigid, inflexible, reliable) |
| unaltered |
| unbending(adjective, certain, limited, definite, inflexible) |
| unblinking(adjective, certain, limited, definite, inflexible) |
| undiversified(adjective, set, regular, normal, even) |
| unfaltering(adjective, certain, limited, definite, inflexible) |
| unflinching(adjective, certain, limited, definite, inflexible) |
| unfluctuating(adjective, normal, even, rigid, inflexible) |
| unmovable(adjective, certain, limited, definite, fixed) |
| unqualified(adjective, certain, limited, definite, inflexible) |
| unremitting |
| unreturnable |
| unsusceptible |
| unwavering(adjective, secure, certain, steady, limited) |
| well-proportioned(adjective, normal, even, rigid, inflexible) |
| cast-iron(inflexible, intent, hard-and-fast) |