The Collaborative International Dictionary of English v.0.48:

Exedra \Ex"e*dra\ ([e^]ks"[-e]*dr[.a]), n.; pl. Exedr[ae]
   ([e^]ks"[-e]*dr[=e]). [L., fr. Gr 'exe`dra; 'ex out + "e`dra
   seat.]
   1. (Class. Antiq.) A room in a public building, furnished
      with seats.
      [1913 Webster]

   2. (Arch.)
      (a) The projection of any part of a building in a rounded
          form.
      (b) Any out-of-door seat in stone, large enough for
          several persons; esp., one of curved form.
          [1913 Webster]