sitter

(noun) Dutch astronomer who calculated the size of the universe and suggested that it is expanding (1872-1934). Synonyms: Sitter, Willem de Sitter.

(noun) an organism (person or animal) that sits.

(noun) a person engaged to care for children when the parents are not home. Synonyms: babysitter, baby-sitter.

(noun) a person who poses for a painter or sculptor. Synonyms: artist's model.

(noun) a domestic hen ready to brood. Synonyms: brood hen, broody, broody hen, setting hen.