Chiefly with defining word. A person who has charge of or looks after a specified thing or operation, esp. in the course of employment. Without…

a person engaged to look after a baby or babies, esp. while their parents or guardians are at work; cf. childminder, n. minder, n. 4a.

A person engaged to look after a child or children while the parents or guardians are out. Cf. sitter, n.1 2b(d).

A person who takes care of a child or children, esp. in the temporary absence of a parent or guardian; spec. a person registered with the local…

Non-literal uses. A babysitter. Also: a person who takes care of a pet, property, etc., in the absence of the owner (cf. -sitter, comb._form).

A babysitter. Cf. sitter, n.1 2b(d). Now rare.