登山自行车很适合凹凹坑坑的城市街道。

Mountain bicycles are great on pot-holed city streets.

youdao

看看你的枕头，太旧了，里面装的东西还一块块凹凹凸凸的，我想你该考虑换个新的了。

Take a look at your pillow, too. If it's old and the filling is clumping up, it might be time to treat yourself to a new one.

youdao

Since this is a concave function, it's not just the expected value.

由于这是一条凹曲线,它不只是期待值

耶鲁公开课 - 金融市场课程节选

We all know that in 2006 the car had a lot of scratches and it got bended in one side and pretty sorry looking in terms of the scrapes and the paint job and the rust.

我们都知道,2006年的车有很多刮痕,一边车身还凹了,很旧的样子,到处是刮痕，油漆脱落，生锈。

耶鲁公开课 - 死亡课程节选