| unfailing(adjective, strong, firm, determined, steady) |
| unshakeable(adjective, resolute) |
| willful(adjective, tough, firm, difficult, resist) |
| adherent(firm, true, fixed, constant, tacky) |
| assiduous |
| brave(adjective, strong, tough, determined, vigorous) |
| contumacious(adjective, tough, firm, persistent, obstinate) |
| deliberate(adjective, intense, determined, resolute, focused) |
| powerful(adjective, strong, sound, tough, fit) |
| recollective |
| resistant(adjective, strong, determined, resolute, sturdy) |
| sedulous |
| self-willed(adjective, tough, firm, difficult, wild) |
| serious(adjective, strong, firm, determined, resolute) |
| solid(adjective, strong, sound, secure, tough) |
| spirited(adjective, determined, resolute, brave, daring) |
| stringy(adjective, tenacity) |
| substantial(adjective, strong, sound, tough, fit) |
| tacky(adjective, secure, thick, sticky, viscous) |
| thorough(adjective, precise, resolute, meticulous) |