To keep in possession or use.
To employ by paying a retainer.
To hold back (a pupil) instead of allowing them to advance to the next class or year.
To keep in one's pay or service.
To hold secure.
To keep (a physical object that one has obtained) to oneself rather than giving it back to its owner.
To stay back.
To keep (information, assent etc) to oneself rather than revealing it.