Intrados

[in'treidɒs]

(noun.) the interior curve of an arch.

Editor: Woodrow--From WordNet

(n.) The interior curve of an arch; esp., the inner or lower curved face of the whole body of voussoirs taken together. See Extrados.

Checker: Williams

n. (archit.) the interior or lower line or surface of an arch or vault:—opp. to Extrados the exterior or upper curve.

Edited by Fergus