1 to get into a comfortable position, sitting or lying 舒适地坐下或躺下

2 to start having a quieter way of life, especially by staying in the same place or getting married 过更宁静的生活（尤指定居某地或结婚等）；安家落户；安顿下来: She had a number of jobs abroad before she eventually settled down. 她最终安顿下来前，曾在国外做过一些不同的工作。

3 to become calm and quiet 安静下来: Settle down! It's time to start the lesson. 大家安静！现在开始上课。