| compressed(verb, adjective, strong, hard) |
| concentrated(verb, adjective, strong, hard) |
| compact(adjective, strong, hard, firm) |
| packed(verb, adjective, strong, hard) |
| solid(adjective, strong, hard, firm) |
| consolidated(verb, adjective, strong, hard) |
| dense(adjective, strong, hard, firm) |
| firm(adjective, strong, hard, solid) |
| hard(adjective, strong, firm, solid) |
| hardened(verb, adjective, strong, hard) |
| impenetrable(adjective, strong, hard, firm) |
| strong(adjective, hard, firm, substantial) |
| adamantine(adjective, strong, hard, firm) |
| callous(adjective, strong, hard, firm) |
| hard-handed(adjective, strong, hard, compact) |
| hard as nails(expression, adjective, idiom, strong) |
| indurate(adjective, strong, hard, firm) |
| indurated(adjective, strong, hard, firm) |
| inflexible(adjective, strong, hard, firm) |
| iron(adjective, strong, hard, firm) |