回複：married up 可以理解為“是嫁入豪門”嗎？

我覺得通常指嫁給比自己地位高很多的人, of higher socialeconomic class，像Kate Middleton 嫁給Prince Williams 就是marrying up. 

不過也許口語裏marrying up means marrrying up(to my own expectation) which is exchangable with marrying well.