| hard-line(adjective, persistent, obstinate, insistent, dogged) |
| hard-nosed |
| hard-shell(adjective, persistent, obstinate, insistent, dogged) |
| hard-shelled(adjective, persistent, obstinate, insistent, dogged) |
| hard as nails(expression, adjective, idiom, tough, firm) |
| hardboiled(adjective, serious, resolute, persistent, unwavering) |
| hardheaded(tough, firm, determined, unreasonable, grim) |
| harsh(adjective, cruel, determined, fierce, persistent) |
| high on(expression, adjective, passionate, violent, enthusiastic) |
| hold the fort(expression, adjective, idiom, tough, firm) |
| hold the line(expression, adjective, idiom, tough, firm) |
| immersed |
| immersed in |
| immobile(adjective, intense, cruel, resolute, persistent) |
| immoderate(adjective, passionate, violent, enthusiastic, fervent) |
| impassioned(adjective, passionate, violent, enthusiastic, fervent) |
| impulsive(adjective, passionate, violent, enthusiastic, fervent) |
| incompliant(adjective, tough, severe, firm, harsh) |
| incorrigible(adjective, passionate, violent, enthusiastic, fervent) |
| industrious |