n. An ornamental molding or band following the curve on the underside of an arch.
the GNU version of the Collaborative International Dictionary of English
n. The architectural member surrounding the curved opening of an arch, corresponding to the architrave in the case of a square opening.
n. More commonly, the molding or other ornaments with which the wall face of the voussoirs of an arch is charged.
The Century Dictionary and Cyclopedia
n. An ornamental molding or band of moldings on the face of an arch following the contour of the extrados; an arch-molding. Also called architrave.
Word Usage
"The archivolt that sat above the twenty-foot entrance was inlaid with exquisite gold Arabic calligraphy and the monograms of Sultans Mehmed II and Abdul Aziz I."