D defs.my
Entry 2 senses Webster, 1913

Sitter

/sĭt'-ẽr/ · Sit·ter · IPA /ˈsɪtɚ/
01 n. One who sits; esp., one who sits for a portrait or a bust.
  1. 1.
    One who sits; esp., one who sits for a portrait or a bust.
  2. 2.
    A bird that sits or incubates.