IPA: /ˈsɪtər/
KK: /ˈsɪtər/
A person who takes care of children or a person who poses for a portrait.
The sitter was very patient while the artist painted her portrait.
Sitter → The word is formed from "sit" (from Old English "sittan", meaning to be in a position of rest) and "-er" (meaning a person who). A sitter is a person who is in a position of rest, typically seated.
Think of someone who is 'resting' ('sit') and the '-er' just means a person. A sitter is someone who is resting or seated.