sitter

Short definition from Wiktionary

Noun

1. 1
   Someone who sits, e.g. for a portrait.
2. 2
   One employed to watch or tend something; a babysitter, housesitter, petsitter, etc.
3. 3
   A sitting room.
4. 4
   A participant in a séance.
5. 5
   A broody hen.
6. 6
   A very easy scoring chance.

Proper noun

1. 1
   A surname.
2. 2
   A river in north-east Switzerland, a tributary of the Thur.