n. 对角斜拱

Squinch \Squinch\ (skw[i^]nch), n. [Corrupted fr. sconce.]
(Arch.)
A small arch thrown across the corner of a square room to
support a superimposed mass, as where an octagonal spire or
drum rests upon a square tower; -- called also {sconce}, and
{sconcheon}.