穹隅
Pendentive \Pen*den"tive\, n. [F. pendentif, fr. L. pendere to hang.] (Arch.) (a) The portion of a vault by means of which the square space in the middle of a building is brought to an octagon or circle to receive a cupola. (b) The part of a groined vault which is supported by, and springs from, one pier or corbel.