keep someone back
and hold someone back 1. Lit. to restrain people from moving forward or getting in the way. The police were ordered to keep people back so they wouldn't interfere with the paramedics.
2. Fig. to keep a child in the same grade for an extra year. We asked them to keep John back a year. John was kept back a year in school.
3. Fig. to keep someone from advancing in life. I think that your limited vocabulary is keeping you back. Her lack of computer skills kept her back in her career.
keep someone or something back
to hold someone or something in reserve. Keep back some of the food for an emergency. We are keeping Karen back until the other players have exhausted themselves.
keep (someone, something, or an animal) back (from someone or something)
to make someone, something, or an animal stay in a position away from someone or something. Keep everyone back from the injured lady. Please keep the dogs back from the turtle.