Search Result for "extrados": 
Wordnet 3.0

NOUN (1)

1. the exterior curve of an arch; 



The Collaborative International Dictionary of English v.0.48:

Extrados \Ex*tra"dos\, n. [F.; pref. extra- outside + dos (L.
   dorsum) the back.] (Arch.)
   The exterior curve of an arch; esp., the upper curved face of
   the whole body of voussoirs. See Intrados.
   [1913 Webster]


WordNet (r) 3.0 (2006):

extrados
    n 1: the exterior curve of an arch