| No. | Item | Definition |
|---|---|---|
| 1. | abrasive | rough or unpleasant in manner |
| 2. | acerbic | sharp and critical |
| 3. | advanced | difficult for beginners |
| 4. | arduous | requiring great effort |
| 5. | austere | severe and plain |
| 6. | awkward | difficult to manage |
| 7. | baffling | very confusing |
| 8. | biting | sharply critical or cold |
| 9. | brittle | firm but easily broken |
| 10. | brutal | very difficult or severe |
| 11. | bumpy | not smooth or easy |
| 12. | byzantine | overly complex |
| 13. | calcified | made rigid with calcium |
| 14. | challenging | testing ability or effort |
| 15. | compact | closely packed together |
| 16. | complex | not simple or easy |
| 17. | complicated | difficult to understand |
| 18. | compressed | pressed tightly together |
| 19. | confusing | difficult to understand |
| 20. | convoluted | complicated and confusing |
| 21. | daunting | intimidatingly difficult |
| 22. | demanding | requiring much effort |
| 23. | dense | closely packed or compact |
| 24. | difficult | not easy to do |
| 25. | draconian | extremely severe |
| 26. | elusive | difficult to find or grasp |
| 27. | exacting | demanding precision or effort |
| 28. | fiddly | requiring careful small movements |
| 29. | fierce | intense or aggressive |
| 30. | firm | not soft or yielding |
| 31. | formidable | impressively difficult |
| 32. | fraught | full of difficulty |
| 33. | grueling | extremely tiring and demanding |
| 34. | hairy | dangerous or difficult |
| 35. | hardened | made firm or tough |
| 36. | harsh | severe or unpleasant |
| 37. | heartless | cruel and unkind |
| 38. | heavy | serious or difficult |
| 39. | hellish | extremely unpleasant or difficult |
| 40. | Herculean | requiring enormous effort |
| 41. | impenetrable | difficult to understand |
| 42. | inexorable | impossible to stop or soften |
| 43. | inflexible | not easily bent or changed |
| 44. | insoluble | impossible to solve |
| 45. | intimidating | frighteningly challenging |
| 46. | intractable | very difficult to solve |
| 47. | intricate | complex and detailed |
| 48. | involved | complicated and difficult |
| 49. | killer | extremely difficult |
| 50. | knotty | complicated and difficult |
| 51. | laborious | involving much work |
| 52. | labyrinthine | complicated and confusing |
| 53. | leathery | tough like leather |
| 54. | merciless | showing no mercy |
| 55. | murderous | extremely difficult or unpleasant |
| 56. | mystifying | very puzzling |
| 57. | obscure | not clear or understandable |
| 58. | onerous | burdensome or demanding |
| 59. | opaque | difficult to understand |
| 60. | perplexing | confusing and difficult |
| 61. | petrified | turned stony or rigid |
| 62. | pitiless | showing no pity |
| 63. | problematic | causing difficulty |
| 64. | punishing | extremely demanding or severe |
| 65. | puzzling | difficult to understand |
| 66. | relentless | continuing without easing |
| 67. | resistant | able to withstand force |
| 68. | rigid | not flexible |
| 69. | rigorous | strict and demanding |
| 70. | rocklike | as firm as rock |
| 71. | rocky | full of difficulties |
| 72. | rough | difficult or unpleasant |
| 73. | ruthless | showing no pity |
| 74. | set | firm and fixed |
| 75. | Sisyphean | endlessly difficult and futile |
| 76. | solid | firm and not soft |
| 77. | steely | firm like steel |
| 78. | sticky | difficult or awkward |
| 79. | stiff | not easily bent |
| 80. | stony | like stone; firm |
| 81. | strenuous | requiring vigorous effort |
| 82. | strong | having great force or firmness |
| 83. | tangled | complicated and confused |
| 84. | taxing | requiring great effort |
| 85. | testing | challenging one’s abilities |
| 86. | thorny | difficult and complicated |
| 87. | tortuous | complicated and indirect |
| 88. | tough | difficult or demanding |
| 89. | toughened | made stronger or firmer |
| 90. | tricky | difficult to handle |
| 91. | troublesome | causing problems |
| 92. | trying | difficult to endure |
| 93. | unanswerable | impossible to answer |
| 94. | unbending | not bending or flexible |
| 95. | unforgiving | not allowing mistakes |
| 96. | unmanageable | too difficult to control |
| 97. | unsolvable | not able to be solved |
| 98. | unsparing | severe and unmerciful |
| 99. | unyielding | not giving way |
| 100. | uphill | requiring sustained effort |