男凸女凹传统美
[nán tū nǚ āo chuán tŏng mĕi]
It reflects traditional Chinese thoughts about men and women's compatibility and relationship structure. '男凸女凹' represents Yin-Yang philosophy and gender complementation: convex (Yang) and concave (Yin). Here ‘美’ means beauty, implying this is traditionally considered 'beautiful.'