| No. | Term | Definition |
|---|---|---|
| 1. | Abstruse | hard to understand; obscure |
| 2. | Adverse | unfavorable; creating hardship |
| 3. | Aging | becoming harder over time |
| 4. | Amiably tough | friendly yet hard to handle |
| 5. | Arduous | requiring great effort |
| 6. | Awkward | hard to manage or do |
| 7. | Backbreaking | extremely physically demanding |
| 8. | Baffling | confusing; puzzling |
| 9. | Barbed | sharply critical; hard to take |
| 10. | Byzantine | overly complex; labyrinthine |
| 11. | Challenging | testing one’s abilities |
| 12. | Complicated | made of many parts |
| 13. | Convoluted | twisted; hard to follow |
| 14. | Crabbed | difficult to read or decipher |
| 15. | Crazy-making | deeply frustrating to endure |
| 16. | Crippling | severely limiting; overwhelming |
| 17. | Cumbersome | heavy and hard to carry |
| 18. | Daunting | intimidatingly hard |
| 19. | Demanding | requiring much effort |
| 20. | Dense | hard to penetrate or grasp |
| 21. | Dicey | risky; hard to handle |
| 22. | Discouraging | making effort feel futile |
| 23. | Draggy | slow and hard to get through |
| 24. | Draining | emotionally or physically exhausting |
| 25. | Dreadful | causing dread; unpleasant |
| 26. | Elusive | hard to find or catch |
| 27. | Enigmatic | mysterious; hard to interpret |
| 28. | Exacting | requiring great precision |
| 29. | Excruciating | extremely painful or intense |
| 30. | Exhausting | wearing out energy |
| 31. | Fiddly | requiring careful, small work |
| 32. | Formidable | inspiring fear or respect |
| 33. | Frustrating | causing annoyance and difficulty |
| 34. | Gnarled | twisted; hard to work with |
| 35. | Grim | harsh; difficult to face |
| 36. | Grueling | very tiring and demanding |
| 37. | Hairy | complicated; risky; tricky |
| 38. | Hard | not easy; requiring effort |
| 39. | Hard-fought | won only with effort |
| 40. | Harrowing | deeply distressing; hard to endure |
| 41. | Heavy | burdensome; hard to bear |
| 42. | Herculean | requiring enormous strength |
| 43. | High-stakes | with serious consequences |
| 44. | Horrendous | shockingly bad; hard to endure |
| 45. | Impenetrable | impossible to understand or enter |
| 46. | Inaccessible | hard to reach or use |
| 47. | Inconvenient | causing trouble or difficulty |
| 48. | Incredible | hard to believe or accept |
| 49. | Inflexible | not easily changed or bent |
| 50. | Insoluble | unable to be solved |
| 51. | Intense | extremely demanding or strong |
| 52. | Intractable | hard to control or solve |
| 53. | Intricate | complex with many details |
| 54. | Knotty | complex; full of problems |
| 55. | Labored | done with visible effort |
| 56. | Labyrinthine | maze-like; very complex |
| 57. | Lengthy | taking a long time |
| 58. | Lumpy | uneven; hard to smooth |
| 59. | Maddening | extremely annoying; exasperating |
| 60. | Merciless | unyielding; offering no relief |
| 61. | Mind-bending | extremely hard to grasp |
| 62. | Murky | unclear; hard to see through |
| 63. | Nasty | unpleasantly hard to deal with |
| 64. | Nerve-wracking | causing anxiety and strain |
| 65. | Obdurate | stubborn; hard to influence |
| 66. | Obscure | not clear; hard to understand |
| 67. | Onerous | burdensome; oppressive |
| 68. | Opaque | not transparent; hard to understand |
| 69. | Ordeal-like | like a severe trial |
| 70. | Overwhelming | too much to handle |
| 71. | Painful | causing physical or emotional hurt |
| 72. | Perilous | dangerous; risky |
| 73. | Perplexing | confusing; baffling |
| 74. | Picky | requiring fussy attention |
| 75. | Ponderous | heavy; slow and hard |
| 76. | Problematic | creating difficulties or doubts |
| 77. | Prohibitive | too costly or limiting |
| 78. | Punishing | harshly demanding; exhausting |
| 79. | Puzzling | hard to explain or solve |
| 80. | Rebarbative | unpleasant; hard to accept |
| 81. | Relentless | continuing without easing |
| 82. | Resistant | not easily affected or changed |
| 83. | Rigorous | strict and demanding |
| 84. | Rocky | full of obstacles |
| 85. | Rough | hard; unpleasant; uneven |
| 86. | Rugged | tough; hard-wearing |
| 87. | Severe | very harsh or serious |
| 88. | Spiky | prickly; hard to approach |
| 89. | Sticky | hard to escape or resolve |
| 90. | Stiff | hard to bend or move |
| 91. | Strained | under pressure; difficult |
| 92. | Strenuous | requiring great exertion |
| 93. | Stubborn | hard to move or change |
| 94. | Taxing | demanding; draining |
| 95. | Testing | challenging; revealing weaknesses |
| 96. | Thorny | full of complications |
| 97. | Tough | hard to do or endure |
| 98. | Tricky | requiring care; not straightforward |
| 99. | Troublesome | causing problems; hard to manage |
| 100. | Trying | stressful; hard to endure |