know-it-all /ˈnoətˌɔl/
  假裝博學多聞的人(a.)自稱無所不知的
  Know-it-all n. One who knows everything; hence, a person who makes pretension to great knowledge, especially one whose didactic conversational habit conspicuously reveals his belief that he has superior knowledge on many subjects; a wiseacre; a know-all; -- usually ironical. [Colloq. & pejorative] 
  Note: the use of this term implies that the speaker disapproves of this behavior, and may think that it is unjustified
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  know-it-all
       n : someone who thinks he knows everything and refuses to accept
           advice or information from others [syn: know-all]