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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91. As we set off into the forest, we felt as though we were venturing into the unknown.
92. Unknown to me, she'd organized a party for my birthday.
93. To her the outside world was a totally unknown quantity.
94. The third candidate for the party leadership is a relatively unknown quantity.
95. The verdict was murder by a person or persons unknown.
96. The original picture of the unknown ancient painter took my breath away.
97. The timing of the attack, and its motivations, are unknown.
98. Our aim is to make it easier for young unknown artists to show their work.
99. Their football team bowed out of the competition with unknown reasons.
100. A previously unknown extremist group has said it carried out Friday's bomb attack.
101. He was born in France in 1670 of unknown parentage .
102. Unknown to his wife, Ron had been having an affair.
103. Racism is in some ways just a fear of the unknown.
104. An unknown disease suddenly attacked the crops in this area.
105. The novel starts when a child of unknown parentage is left at the house of the local priest.
106. In algebra the sign x usually denotes an unknown quantity.
107. His ability to make decisions in a crisis is an unknown quantity.
108. He became a person whose whereabouts is unknown to me.
109. The long-term effects of the drug are still an unknown.
110. An unknown actor was penciled in to play the leading role.
111. Thanks to the automobile[sentencedict.com],[http://sentencedict.com/unknown.html] Americans soon had a freedom of movement previously unknown.
112. He lived well, helping the poor, and all other people; he died penniless and unknown.
113. It is not unknown for valuable display items to go, ahem, missing.
114. Life can be likened to a journey with an unknown destination.
115. I could not understand how someone with so many awards could be unknown to me.
116. An unknown man's dismembered body was found by the police in the suburb woods.
117. The movie transformed her almost overnight from an unknown schoolgirl into a megastar.
118. How did you expect us to proceed on such a perilous expedition, through unknown terrain.
119. No one could match the skill of the unknown carver.
120. An unknown terrorist group has claimed responsibility for this morning's bomb attack.
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.