Arch. Also 8 surbast. [repr. F. surbaissè, f. sur- exceedingly = SUPER- 9 b + baissé lowered.] Surbased arch, an arch whose rise is less than half the span. So surbased dome.
1763. Gray, Lett. to Mason, 8 Feb. Roger’s own tomb … has … a wide surbased arch with scalloped ornaments.
1793. Gentl. Mag., May, 422/1. Under each chancel window, nearest the East end, is a surbast arch.
1825. J. Nicholson, Operat. Mechanic, 540. The semicircular are called perfect arches, and those less than a semicircle, imperfect, surbased, or diminished arches. Arches are also called surmounted, when they are higher than a semicircle.
So Surbasement [F. surbaissement], the condition of being surbased.
1833. Crabb, Dict. Gen. Knowl. (ed. 3), Surbasement, the trait of any arch … that describes a portion of an ellipsis.
