One who minds, tends, or watches something such as a child, a machine, or cattle; a keeper.
A monitor assigned by the authorities to someone, such as a foreign visitor (to exercise control over their contacts with the populace) or a journalist or someone who is speaking to journalists (to monitor and control what they say).
A personal bodyguard.
A person who is certified to provide custodial care such as help in walking, bathing, and feeding.