to (cause someone to) be in a position in which the lower part of the body is resting on a seat or other type of support, with the upper part of the body vertical: to sit at a table/desk. to sit in an armchair. to sit on a chair/a horse/the ground. He came and sat (down) next to me.

1. : to cause to be seated : place on or in a seat. often used with down. 2. : to sit on (eggs)