| No. | Item | Definition |
|---|---|---|
| 1. | a blank | something forgotten or unknown |
| 2. | a closed book | something not understood |
| 3. | a mystery | something not understood |
| 4. | a question mark | something uncertain or unknown |
| 5. | ambiguous | having more than one meaning |
| 6. | an enigma | a puzzling, unknown thing |
| 7. | anonymous | not named or identified |
| 8. | arcane | known by few; mysterious |
| 9. | baffling | impossible to understand or explain |
| 10. | blurred | not clear or distinct |
| 11. | clueless | having no idea |
| 12. | cryptic | mysterious or unclear in meaning |
| 13. | doubtful | not certain; open to doubt |
| 14. | dubious | not to be relied on |
| 15. | enigmatic | mysterious and hard to interpret |
| 16. | equivocal | open to more than one meaning |
| 17. | esoteric | understood by a small group |
| 18. | hazy | unclear; not well remembered |
| 19. | ignorant | not knowing about something |
| 20. | impenetrable | hard to understand or interpret |
| 21. | in doubt | not certain; questionable |
| 22. | in question | not certain; being considered |
| 23. | in the dark | not knowing what’s happening |
| 24. | inaccessible | not able to be reached |
| 25. | inconclusive | not leading to a clear result |
| 26. | indeterminate | not precisely known or fixed |
| 27. | indistinct | not clear or sharply defined |
| 28. | inexplicable | unable to be explained |
| 29. | inscrutable | impossible to understand |
| 30. | lost | unable to be found |
| 31. | missing | not present; cannot be found |
| 32. | murky | dark or unclear; confusing |
| 33. | mysterious | hard to explain or understand |
| 34. | nameless | without a name |
| 35. | nebulous | vague and ill-defined |
| 36. | not certain | not definite or sure |
| 37. | not clear | not clear or understood |
| 38. | not confirmed | not verified as true |
| 39. | not determined | not decided or fixed |
| 40. | not established | not proven or set |
| 41. | not identified | not identified or named |
| 42. | not known | not known or understood |
| 43. | not verified | not checked or proven |
| 44. | oblivious | not aware or noticing |
| 45. | obscure | not well known or understood |
| 46. | off the radar | not noticed or tracked |
| 47. | opaque | not clear; hard to understand |
| 48. | open | not decided; still unresolved |
| 49. | out of reach | not accessible or obtainable |
| 50. | out of sight | not visible or seen |
| 51. | out of view | not visible or seen |
| 52. | perplexing | confusing and difficult to grasp |
| 53. | problematic | uncertain or difficult to resolve |
| 54. | puzzling | confusing; hard to understand |
| 55. | questionable | doubtful; not certain |
| 56. | shadowy | vague; not clearly known |
| 57. | unaccounted-for | not explained or accounted for |
| 58. | unascertained | not determined for sure |
| 59. | unavailable | not able to be obtained |
| 60. | unaware | not aware of something |
| 61. | uncertain | not known or definite |
| 62. | uncharted | not mapped or explored |
| 63. | unclear | not clear or understood |
| 64. | uncognized | not recognized or known |
| 65. | unconfirmed | not confirmed or proven |
| 66. | undetected | not detected or discovered |
| 67. | undetermined | not decided or fixed |
| 68. | undiscovered | not yet found or learned |
| 69. | unestablished | not firmly set or proven |
| 70. | unexplained | not explained or understood |
| 71. | unexplored | not yet examined or investigated |
| 72. | unfamiliar | not known from experience |
| 73. | unfathomed | not understood or explored |
| 74. | unfindable | not able to be found |
| 75. | unheard-of | not known or encountered |
| 76. | unidentified | not identified or named |
| 77. | uninformed | not informed about something |
| 78. | uninitiated | not informed or experienced |
| 79. | unlearned | not learned or known |
| 80. | unlisted | not included on a list |
| 81. | unmapped | not charted or recorded |
| 82. | unnamed | not given a name |
| 83. | unnoted | not noticed or recorded |
| 84. | unnoticed | not noticed or observed |
| 85. | unobserved | not seen or detected |
| 86. | unplumbed | not explored or understood |
| 87. | unproven | not shown to be true |
| 88. | unrecognized | not recognized or acknowledged |
| 89. | unrecorded | not written down or logged |
| 90. | unregistered | not officially recorded |
| 91. | unreported | not reported or made known |
| 92. | unresolved | not settled or answered |
| 93. | unseen | not seen or noticed |
| 94. | unsubstantiated | not supported by evidence |
| 95. | unsure | not certain or confident |
| 96. | untraceable | impossible to trace or track |
| 97. | untrackable | not able to be tracked |
| 98. | untried | not tested or experienced |
| 99. | unverified | not confirmed as true |
| 100. | vague | not clearly expressed or known |
