extrados

From French extradossé (“outer curve”) from Latin extra (“outside”) + dos (“back”) (from Latin dorsum).

extrados (plural extradoses or extrados)

1. (architecture) The outer or upper curve of an arch.
   • 1954 January, “Strengthening of Coquet Viaduct”, in Railway Magazine, page 19:

     The two lower rows of tubes at each end pier were then drilled through to the extrados of the brickwork to act as weep holes and assist in the drainage from the backs of the arches.

• intrados

• extradosed

Borrowed from French extrados.

extrados n (plural extradosuri)

1. extrados