angle-capital

from The Century Dictionary.

• noun In Grecian Ionic arch., a capital on the corner column of a portico, having volutes on both front and flank, with the volutes which would come together at the angle of the entablature combined and turned outward on the line of the diagonal between the planes of the frieze on front and flank.
• noun In Roman and modern Ionic architecture, the capital of a similarly situated column, having four volutes, of which each is on a diagonal of the abacus of the capital.