the narrow space between a person's breasts that is seen when they wear 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。

(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。