What is the meaning of Sitter?

Someone who sits, e.g. for a portrait.

One employed to watch or tend something; a babysitter, housesitter, petsitter, etc.

A sitting room.

A participant in a séance.

A broody hen.

A very easy scoring chance.

Someone who accompanies a person who is taking a psychedelic drug, to provide reassurance in case of a bad trip.

present of sitte

(non-standard since 2012) present tense of sitje

present indicative of sitta

Source: wiktionary.org