| Solution | Length | |
|---|---|---|
| 3 letters | ||
| set | 3 | |
| 4 letters | ||
| iron | 4 | |
| true | 4 | |
| hard | 4 | |
| sure | 4 | |
| 5 letters | ||
| stiff | 5 | |
| tight | 5 | |
| rigid | 5 | |
| stern | 5 | |
| tough | 5 | |
| stony | 5 | |
| 6 letters | ||
| steely | 6 | |
| severe | 6 | |
| strict | 6 | |
| steady | 6 | |
| unkind | 6 | |
| 7 letters | ||
| RIGIDLY | 7 | |
| adamant | 7 | |
| staunch | 7 | |
| settled | 7 | |
| puritan | 7 | |
| unmoved | 7 | |
| precise | 7 | |
| 8 letters | ||
| ungiving | 8 | |
| unshaken | 8 | |
| ironclad | 8 | |
| obdurate | 8 | |
| stubborn | 8 | |
| rigorous | 8 | |
| resolute | 8 | |
| puristic | 8 | |
| standpat | 8 | |
| 9 letters | ||
| hardnosed | 9 | |
| unbending | 9 | |
| obstinate | 9 | |
| unmovable | 9 | |
| tenacious | 9 | |
| steadfast | 9 | |
| ROCKBOUND | 9 | |
| UNDEFINED | 9 | |
| unpliable | 9 | |
| 10 letters | ||
| relentless | 10 | |
| stationary | 10 | |
| UNAFFECTED | 10 | |
| determined | 10 | |
| UNYIELDING | 10 | |
| UNSWERVING | 10 | |
| 11 letters | ||
| UNAVOIDABLE | 11 | |
| unrelenting | 11 | |
| straitlaced | 11 | |
| UNSTOPPABLE | 11 | |
| UNFLAPPABLE | 11 | |
| unalterable | 11 | |
| UNRECEPTIVE | 11 | |
| puritanical | 11 | |
| hardandfast | 11 | |
| PROCRUSTEAN | 11 | |
| 12 letters | ||
| UNCHANGEABLE | 12 | |
| unresponsive | 12 | |
| recalcitrant | 12 | |
| 13 letters | ||
| unpreventable | 13 | |
| STRAIGHTLACED | 13 | |
| unsusceptible | 13 | |
| unpersuadable | 13 | |
| 14 letters | ||
| UNCOMPROMISING | 14 | |
| uncontrollable | 14 | |