Definition of "metope"

There's a second plate of that metope that shows the full figures of both Perseus and Medusa and includes the winged horse Pegasus that was born of Medusa's blood.

1996, Russell Hoban, Fremder, Bloomsbury, published 2003, page 117

Architects working on the recent restoration programme have found clear evidence that in its first design the building featured just a row of metope panels over the east and west entrances, where the frieze now runs […] .

2002, Mary Beard, The Parthenon, Profile Books, published 2010, page 128