euphemism       
noun [ C or U ]  language uk/ˈjuː.fə.mɪ.zəm/ us/ˈjuː.fə.mɪ.zəm/
 委婉语,委婉说法
a word or phrase used to avoid saying an unpleasant or offensive word
  "Senior citizen" is a euphemism for "old person". “年长公民”是“老年人”的委婉说法。 
 The article made so much use of euphemism that often its meaning was unclear. 这篇文章用了太多的委婉语,以至于意思常常不甚明了。