Main Entry: ex·tra·dos

Pronunciation: \ˈek-strə-ˌdäs, -ˌdō; ek-ˈstrā-ˌdäs\

Function: noun

Inflected Form(s): plural ex·tra·dos·es \-ˌdä-səz\ or ex·tra·dos \-ˌdōz, -ˌdäs\

Etymology: French, from Latin extra + French dos back — more at dossier

Date: 1772

: the exterior curve of an arch — see arch illustration