the world > physical sensation > cleanness and dirtiness > sanitation > privy or latrine > [noun] > water-closet or lavatory > W.C. appliances > seat of (2)
(a) a seat for a dressing table; (b) an approximately oval ring of plastic or wood fitting the top of a toilet bowl, typically hinged at the back…
In narrower sense: That part (of a chair, saddle, etc.) upon which its occupant sits. Also spec. of a lavatory.