| thorough(adjective, complete, severe, harsh, pure) |
| unadaptable(adjective, set, hard, stiff, resolute) |
| unbreakable(adjective, strong, hard, severe, firm) |
| wooden(adjective, hard, correct, firm, solid) |
| Draconian(adjective, tough, severe, firm, harsh) |
| Spartan(adjective, severe) |
| aloof(adjective, cool, tough, firm, fair) |
| bovine(adjective, determined, resolute, obstinate, uncompromising) |
| brass-bound(adjective, determined, resolute, obstinate, uncompromising) |
| bull-headed(adjective, determined, resolute, obstinate, uncompromising) |
| dead set(expression, adjective, tough, severe, firm) |
| difficult(adjective, hard, tough, severe, rough) |
| distant(adjective, tough, firm, cold, unfriendly) |
| extreme(adjective, convention) |
| faithful(adjective, correct, solid, intense, exact) |
| finical |
| hardened(adjective, strong, hard, tough, firm) |
| icy(adjective, cool, severe, cold, detached) |
| immobile(adjective, secure, intense, still, steady) |
| ironclad(adjective, set, hard, severe, cruel) |