Definition of "sitter"

The photograph caused a stir last week because it was shortlisted for the National Portrait Gallery’s prestigious Taylor Wessing prize, despite the rule that “all photographs must have been taken by the entrant from life and with a living sitter”.However realistic Erica may be, and to me she looks more like a sex doll than a real person, she was certainly not a living sitter.

2017 September 10, Nigel Warburton, “What does a portrait of Erica the android tell us about being human?”, in The Observer‎

"The sitters had better just take their own places," said the medium.

1925 July – 1926 May, A[rthur] Conan Doyle, “(please specify the chapter number)”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019

Aaron Ramsey, a hero last season against Hull, missed a sitter at the end of normal time that would have made the game safe and must have been relieved that his shot against a post from four yards out did not cost his side more dearly.

2015 April 18, Paul Wilson, The Guardian‎