| intrepid(adjective, strong, tough, firm, energetic) |
| mettlesome(adjective, energetic, resolute, forceful, courageous) |
| perseverant |
| pronounced(verb, adjective, judged) |
| pushy(adjective, clear, tough, severe, energetic) |
| qualified(limited, restricted) |
| rigorous(adjective, severe, harsh, solid, intense) |
| sedulous(adjective, assiduous) |
| specific(adjective, strong, certain, definite, resolved) |
| spirited(adjective, strong, tough, energetic, active) |
| stable(adjective, good, strong, easy, flat) |
| stated(verb, adjective, strong, flat, firm) |
| tested(verb, experimented) |
| uncompliant(adjective, tough, firm, resolute, stubborn) |
| unconquerable(adjective, persistent, obstinate, insistent, dogged) |
| unequivocal(adjective, good, clear, strong, firm) |
| unmanageable(adjective, tough, firm, persistent, obstinate) |
| unmistakable(adjective, plain) |
| unshaken(adjective, strong, flat, firm, solid) |
| validated(verb, evinced) |