Keep tabs on (someone or something)

To watch or check or observe someone or something.We are keeping tabs on the spending of the sales department.

Keep still

To not move.I tried to keep still during the long lecture.

Keep (something) under wraps

To keep something concealed (until some future date).We plan to keep our plans for the new project under wraps.

Keep (something) under one`s hat

To keep a secret, to not tell something.My coworker will not say where he is going for his holiday. He wants to keep it under his hat.

Keep (something) to oneself

To keep something a secret.I asked my friend to keep the news to herself.

Keep (something) down keep down (something)

To keep food in one's stomach (without vomiting it up when sick).The child was sick and found it difficult to keep his food down.

Keep (someone) up keep up (someone)

To prevent someone from going to bed.My neighbors kept me up last night with their loud music.

Keep (someone or something) still/quiet

To make someone or something silent or less noisy.The mother had a hard time keeping her child still in the airplane.

Keep (someone) posted

To keep someone informed or up-to-date about something.I asked my friend to keep me posted about his new job and address.

Keep (someone) on tenterhooks

To keep someone anxious or in suspense.I was kept on tenterhooks as I waited to hear the results of my exam.