keep someone down—
1. (also: hold someone down) cause a person to remain in a lower position:
- John tried to look in that direction but a crisscrossing hail of laser fire kept him down.
2. (also: hold someone down) oppress or hold back a person:
- He told me that “every company” he had worked for had incompetent management and was trying to keep him down.
3. (UK) make a child remain in the same class for a second year:
- If she failed her examinations again, Jane would be kept down next year.
keep someone under—
1. cause a person to remain beneath smth.:
- I was filming when I went over the falls and the white water kept me under nearly all the way to the beach.
2. = keep someone down 2:
- Everywhere you heard the leaders saying, “It is going to be very difficult to keep the people under.”
3. make a person remain unconscious (under the action of anesthesia):
- He is under more sedation…. They will keep him under until at least late tomorrow.
See also: hold someone up / keep someone up.