Definition of "narthex"

we were in the antechamber, called the narthex, which runs across the front of any Byzantine church [...].

1942, Rebecca West, Black Lamb and Grey Falcon, Canongate, published 2006, page 637

One of these was Cardinal Jacopo Stefaneschi, [...] who had now conceived ambitious plans for paintings to decorate the entire narthex, or entrance porch, of Avignon's ancient cathedral.

2007, Edwin Mullins, The Popes of Avignon, Blue Bridge, published 2008, page 87

“Cinco,” Marco bellowed now, hurrying across the narthex to give him a hearty handshake, which Cinco returned without enthusiasm.

2012, Melissa F. Miller, chapter 42, in Irretrievably Broken (The Sasha McCandless Series), e-book edition, volume 1, Brown Street Books, page 11642