keep down
verb
Definitions
To repress.
Example: China keeps down her dissidents very efficiently.
To restrain or control (a sound).
Example: Keep it down in there! Some of us are trying to sleep!
To cause not to increase or rise.
Example: It is essential to keep the numbers down to avoid overcrowding.
Not to vomit.
Example: It is difficult to keep anything down when you have the flu.