| mulish(adjective, strong, tough, firm, resist) |
| retentive(adjective, strong, unyielding, sticky, retention) |
| rigid(adjective, determined, resolute, persistent, obstinate) |
| uncompromising(adjective, tough, firm, determined, resolute) |
| unfaltering(adjective, strong, firm, intense, deliberate) |
| indefatigable(adjective, strong, tough, fit, firm) |
| fixed(adjective, strong, sound, secure, tough) |
| resolved(adjective, strong, flat, firm, determined) |
| strong(adjective, sound, secure, tough, fit) |
| intransigent(adjective, strong, firm, determined, unreasonable) |
| sticky(adjective, secure, determined, thick, coherence) |
| stiff(adjective, strong, determined, resolute, persistent) |
| tireless(adjective, strong, firm, determined, steady) |
| glutinous(adjective, secure, tough, thick, tacky) |
| insistent(adjective, determined, resolute, obstinate, uncompromising) |
| refractory(adjective, tough, firm, difficult, wild) |
| stalwart(adjective, strong, sound, tough, fit) |
| strong-willed(adjective, strong, firm, intense, deliberate) |
| unflagging(adjective, strong, tough, fit, firm) |
| viscous(adjective, secure, tough, thick, tacky) |