behind the proscenium in a theater, esp. in the wings or dressing rooms.

toward the rear of the stage; upstage.

out of view of the public; in private; behind the scenes

Many of the deals were made backstage at the convention.

located or occurring backstage.

of or pertaining to activities unknown to the public.

of or pertaining to the private lives of people in the entertainment industry

backstage gossip.

Theater . a backstage area.