thrust stage

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A stage that extends into the audience's portion of a theater beyond the usual location of the proscenium and often has seats facing it on three sides.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a theater stage that extends out into the audience's part of a theater and has seats on three sides