/ek"streuh dos', -dohs', ek stray"dos, -dohs/ , n. , pl. extrados /-dohz', -dohz/ , extradoses . Archit.
the exterior curve or surface of an arch or vault. Also called back . Cf. intrados . See diag. under arch .
[ 1765-75; extra- EXTRA- + dos back ( dorsum DORSUM ]