a basin for washing the hands (`wash-hand basin' is a British expression)
a bathroom sink that is permanently installed and connected to a water supply and drainpipe; where you can wash your hands and face; "he ran some water in the basin and splashed it on his face"
in or to a backstage area of a theater; "costumes were changed backstage"
out of view of the public; behind the scenes; "Working backstage to gain political support for his proposal"; "many private deals were made backstage at the convention"