'sit down' definitions:

Definition of 'sit down'

(from WordNet)
verb
Take a seat [syn: sit down, sit] [ant: arise, get up, rise, stand up, uprise]
verb
Show to a seat; assign a seat for; "The host seated me next to Mrs. Smith" [syn: seat, sit, sit down]
verb
Be seated [syn: sit, sit down] [ant: lie, stand, stand up]

Synonyms of 'sit down'

From: Moby Thesaurus