| nonelastic |
| pertinacious(adjective, determined, resolute, obstinate, uncompromising) |
| pig-headed(adjective, determined, resolute, obstinate, uncompromising) |
| relentless(adjective, determined, resolute, obstinate, uncompromising) |
| resistant(adjective, hard, firm, solid, determined) |
| set in stone(expression, adjective, idiom, tough, severe) |
| standing pat(expression, adjective, tough, firm, determined) |
| tenacious(adjective, determined, resolute, obstinate, uncompromising) |
| unchangeable |
| unrelenting(adjective, determined, resolute, obstinate, uncompromising) |
| unswayable(adjective, tough, firm, determined, distant) |
| compact(adjective, hard, solid, rigid) |
| compressed(adjective, hard, tough, solid, rigid) |
| concentrated(adjective, hard, tough, solid, rigid) |
| condensed(adjective, hard, tough, solid, rigid) |
| ductile(adjective, softness) |
| extensile |
| flaccid(adjective, drooping) |
| frail |
| impliable(adjective, hard, firm, solid, stiff) |