Antonym: known. Similar words: flunk, skunk, chunk, trunk, know, sunken, debunk, knob. Meaning: [ʌnˈnəʊn] 
n. 1. an unknown and unexplored region 2. anyone who does not belong in the environment in which they are found 3. a variable whose values are solutions of an equation. adj. 1. not known 2. being or having an unknown or unnamed source 3. not known to exist 4. not famous or acclaimed 5. not known before.
n. 1. an unknown and unexplored region 2. anyone who does not belong in the environment in which they are found 3. a variable whose values are solutions of an equation. adj. 1. not known 2. being or having an unknown or unnamed source 3. not known to exist 4. not famous or acclaimed 5. not known before. 
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61. The immediate cause of death is unknown.
62. We decided to chart out that unknown area.
63. His whereabouts are / is still unknown.
64. The common household fork was nearly unknown in antiquity.
65. The famous player went down to an unknown player.
66. His work is practically unknown here.
67. Unknown to me, he had already signed the agreement.
68. She was then still comparatively unknown.
69. The motive for the killing is unknown.
70. He was an unknown writer.
71. We resist change because of fear of the unknown.
72. Unknown thieves had forced their way into the apartment.
73. Ignorance of people brings fear, fear of the unknown.
74. The provenance of the paintings is unknown.
75. The ultimate fate of the captured troops is unknown.
76. Our new director is still an unknown quantity.
77. The exact location of the hostages is unknown.
78. A young unknown played the leading role.
79. Exactly what transpired remains unknown.
80. For some unknown reason , Mark quit his job and moved to Greece.http://Sentencedict.com
81. As recently as six months ago her name was almost unknown in Britain.
82. Local people live in fear of this unknown sex beast.
83. The new sales director is still a bit of an unknown quantity.
84. The star of the film is a previously unknown actor.
85. The director took a calculated risk in giving the film's main role to an unknown actor.
86. A hundred years ago coronary heart disease was virtually unknown in Europe and America.
87. The studio chiefs wanted a marquee name in the lead role, not some unknown.
88. Starting her own business was a lurch into the unknown.
89. He cites the works of two otherwise unknown authors, the originals of these works having been lost.
90. Largely unknown in his lifetime, Mendel's discoveries earned him posthumous fame.
More similar words: flunk, skunk, chunk, trunk, know, sunken, debunk, knob, drunken, knock, junk mail, hunker down, know about, knock out, knock off, well-known, well known, knock down, knowledge, doorknob, hunkered down, acknowledge, acknowledgement.