Get something under control 使……在控制下 的意思。
例句：
Everything is under control.
一切尽在掌握。
We’ve got the fire under control.
我们已经把火控制住了。
The doctor told me she had the disease under control.
医生跟我说了病情已经被控制住了。
You should learn to keep your temper under control.
你应该学会控制自己的脾气。
相反的：
get something out of control 不在控制下
例句：
We finally called the cops when things got out of control.
当事情完全失控的时候，我们给警察打了电话。
Gosh! My weight is out of control.
我体重又胖了。