cleavage  
noun [ C or U ] uk/ˈkliː.vɪdʒ/ us/ˈkliː.vɪdʒ/
  (BODY AREA)      
  (妇女穿低胸服时露出的)乳沟
the narrow space between a woman's breasts, that is seen when she wears a piece of clothing that does not cover the top of them
  Clare was wearing a low-cut dress that showed off her cleavage. 克莱尔穿了件低胸长裙,露出乳沟。 
   (DISAGREEMENT)      
 formal差异;分歧 
(a) division or disagreement
  There is a marked cleavage between the parties about the government's defence policy. 对于政府的国防政策,党派间存在着明显的分歧。