as flat as an airport runway
平得如机场跑道。。。哈哈哈。“长平公主而已”---你知道是什么意思吗? 如机场跑道那么平---自嘲没身材。你懂的。 如果你懂广东话会比较容易理解。《帝女花》里有一个长平公主。
Some girls think they don't have a nice figure or they think they are not well-propotioned enough, they would mock at themselves this way.