| indefatigable(adjective, strong, tough, continue) |
| staunch(adjective, strong, tough, firm) |
| tenacious(adjective, strong, tough, firm) |
| firm(adjective, strong, tough, solid) |
| strong(adjective, sound, tough, firm) |
| vigorous(adjective, strong, sound, tough) |
| stalwart(adjective, strong, sound, tough) |
| hearty(adjective, strong, healthy, well) |
| rugged(adjective, strong, sound, tough) |
| tough(adjective, strong, sound, firm) |
| vital(adjective, strong, tough, lively) |
| brawny(strong, healthy, well, robust) |
| hale(strong, healthy, well, robust) |
| hardy(adjective, strong, tough, lively) |
| lusty(adjective, strong, sound, tough) |
| muscular(strong, healthy, well, robust) |
| peppy(adjective, strong, tough, lively) |
| potent(adjective, strong, tough, lively) |
| powerful(adjective, strong, sound, tough) |
| robust(strong, active, healthy, well) |