| strait-laced(adjective, tough, correct, severe, firm) |
| demanding(adjective, hard, tough, easy, severe) |
| formal(adjective, tough, correct, severe, firm) |
| implacable(adjective, mean, strong, hard, tough) |
| resolved(adjective, severe, harsh, cruel, determined) |
| tenacious(adjective, determined, resolute, persistent, obstinate) |
| unswayable(adjective, hard, determined, resolute, obstinate) |
| grim(adjective, strong, hard, tough, severe) |
| standing pat(adjective, determined, resolute, obstinate, uncompromising) |
| unchanging(adjective, set, severe, harsh, cruel) |
| dogged(adjective, mean, hard, harsh, cruel) |
| hanging tough(expression, adjective, mean, hard, determined) |
| intractable(adjective, tough, firm, persistent, obstinate) |
| meticulous(adjective, hard, correct, severe, rough) |
| mulish(adjective, mean, strong, hard, tough) |
| steely(adjective, strong, hard, tough, firm) |
| tense(adjective, hard, firm, solid, stiff) |
| uncompliant(adjective, resist, determined, resolute, obstinate) |
| incompliant(adjective, tough, severe, firm, resist) |
| prim(adjective, proper, stiff, particular, solemn) |