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| ultimatum | 
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| n.  (최후 통첩) last offer; final statement of terms made by one party to another | 
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| ultrasonic | 
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| a. Syn. supersonic (초음파) supersonic; higher in frequency than the range of sound perceptible to the human ear | 
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| unadorned | 
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| a. Syn. plain; unembellished (발전을) without adornment; simple or plain; not admirable | 
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| unbearable | 
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| a. Syn. unendurable; intolerable (견딜) unendurable; so unpleasant, distasteful, or painful as to be intolerable | 
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| unbroken | 
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| a. Syn. uninterrupted; intact (깨지지) continuous, without interruption; intact | 
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| uncharted | 
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| a.  (미지) not surveyed or investigated; not charted or recorded on a map or plan | 
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| unconventional | 
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| a. Syn. uncommon; unorthodox (패딩턴) not conforming to accepted rules or standards | 
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| uncover | 
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| v. Syn. reveal; expose; disclose (밝히기) remove the cover from; expose; disclose | 
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| underestimate | 
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| v. Syn. undervalue (과소 평가) make too low an estimate of the quantity; undervalue | 
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| underlying | 
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| a. Syn. fundamental; implicit (기본) lying under or beneath something; basic; implicit; taking precedence; prior |