| No. | Item | Definition |
|---|---|---|
| 1. | abrasive | harsh in manner |
| 2. | adamant | refusing to be persuaded |
| 3. | arduous | requiring great effort |
| 4. | backbreaking | extremely hard physical work |
| 5. | battle-hardened | made tough by experience |
| 6. | bleak | harsh and discouraging |
| 7. | brawny | physically strong |
| 8. | brutal | extremely harsh or cruel |
| 9. | bulletproof | highly resistant to criticism |
| 10. | bullheaded | stubborn and unreasonable |
| 11. | burdensome | hard to bear |
| 12. | callous | emotionally hardened |
| 13. | cast-iron | extremely certain or strong |
| 14. | challenging | demanding effort or skill |
| 15. | cold-blooded | without pity or feeling |
| 16. | complex | having many difficult parts |
| 17. | complicated | not simple or straightforward |
| 18. | cruel | causing pain deliberately |
| 19. | daunting | seeming hard to face |
| 20. | demanding | requiring much effort |
| 21. | determined | firm in purpose |
| 22. | difficult | not easy to do |
| 23. | dogged | stubbornly persistent |
| 24. | durable | able to last long |
| 25. | exacting | requiring great care |
| 26. | ferocious | savagely fierce |
| 27. | fierce | intensely aggressive or strong |
| 28. | firm | not soft or yielding |
| 29. | flinty | hard and unemotional |
| 30. | forceful | strong and assertive |
| 31. | formidable | inspiring fear or respect |
| 32. | game | brave under pressure |
| 33. | grim | harsh and forbidding |
| 34. | gritty | showing courage and resolve |
| 35. | grueling | extremely tiring and difficult |
| 36. | hard | difficult or firm |
| 37. | hardened | made less sensitive |
| 38. | hardhearted | lacking sympathy or kindness |
| 39. | hardy | able to endure hardship |
| 40. | harrowing | extremely distressing |
| 41. | harsh | severe or unpleasant |
| 42. | headstrong | determined to do own way |
| 43. | heartless | without compassion |
| 44. | impenetrable | hard to understand or enter |
| 45. | impervious | not affected or penetrated |
| 46. | implacable | unable to be appeased |
| 47. | indomitable | impossible to defeat |
| 48. | inflexible | not easily changed |
| 49. | intense | extreme in degree |
| 50. | intractable | hard to control or solve |
| 51. | ironclad | very strong and secure |
| 52. | knotty | difficult to solve |
| 53. | laborious | requiring much work |
| 54. | leathery | tough and weathered |
| 55. | mean | unkind or harsh |
| 56. | merciless | showing no pity |
| 57. | mulish | stubborn like a mule |
| 58. | muscular | powerful and strong |
| 59. | nasty | unpleasant or difficult |
| 60. | no-nonsense | practical and strict |
| 61. | obdurate | stubbornly refusing to change |
| 62. | obstinate | stubbornly difficult to move |
| 63. | oppressive | cruelly burdensome or harsh |
| 64. | pitiless | without compassion or mercy |
| 65. | plucky | showing brave determination |
| 66. | powerful | having great strength |
| 67. | punishing | causing severe strain |
| 68. | relentless | unceasing and severe |
| 69. | resilient | able to recover quickly |
| 70. | resolute | firmly determined |
| 71. | rigid | stiff and unbending |
| 72. | robust | strong and healthy |
| 73. | rough | harsh or uneven |
| 74. | rugged | strong and durable |
| 75. | ruthless | cruel and determined |
| 76. | severe | very serious or harsh |
| 77. | stern | serious and severe |
| 78. | sticky | awkwardly difficult |
| 79. | stiff | hard to do or move |
| 80. | stoic | enduring pain without complaint |
| 81. | strenuous | needing much exertion |
| 82. | strict | firmly enforcing rules |
| 83. | sturdy | strongly built and solid |
| 84. | taxing | draining effort or strength |
| 85. | tenacious | persistent and determined |
| 86. | thick-skinned | not easily offended |
| 87. | thorny | full of difficulties |
| 88. | tricky | difficult to handle |
| 89. | trying | difficult and stressful |
| 90. | unbreakable | not able to be broken |
| 91. | uncompromising | not making concessions |
| 92. | unsentimental | not guided by feelings |
| 93. | unsparing | severe and not lenient |
| 94. | unyielding | not giving way |
| 95. | uphill | difficult to achieve |
| 96. | vigorous | strong and energetic |
| 97. | watertight | secure against challenge |
| 98. | weighty | serious or burdensome |
| 99. | wilful | stubbornly self-willed |
| 100. | wiry | thin but strong |