sitter

noun7

1. •
   Someone who sits, e.g. for a portrait.
2. •
   One employed to watch or tend something; a babysitter, housesitter, petsitter, etc.

   • It's always such a pain to get a sitter on short notice.
3. •
   Someone who accompanies a person who is taking a psychedelic drug, to provide reassurance in case of a bad trip.
4. •
   (slang) A very easy scoring chance.

   • How could he miss that? It was an absolute sitter!
5. •
   A participant in a séance who is not a medium.

   • "The sitters had better just take their own places," said the medium. — 1925
6. •
   A broody hen.
7. •
   A sitting room.