| implacable(adjective, strong, hard, tough, severe) |
| impulsive(determined, stubborn, reckless, heedless, impetuous) |
| inclement |
| incompatible(adjective, severe, bleak, stark, austere) |
| indelible |
| inflexible(adjective, strong, hard, tough, severe) |
| inhospitable(adjective, severe, bleak, stark, austere) |
| inquisitorial |
| insensible(adjective, strong, hard, tough, sturdy) |
| inured(adjective, confirmed) |
| jagged(adjective, severe, bleak, stark, austere) |
| jangling(adjective, severe, bleak, stark, austere) |
| jarring(adjective, severe, bleak, stark, austere) |
| long-established(adjective, confirmed) |
| mean(adjective, severe, sharp, nasty, bleak) |
| nasty(adjective, severe, sharp, bleak, stark) |
| noisy(adjective, severe, bleak, stark, austere) |
| not smooth(expression, adjective, severe, bleak, stark) |
| obdurate(adjective, strong, hard, tough, sturdy) |
| obstinate(determined, impulsive, stubborn, reckless, impetuous) |