spandrel

The roughly triangular space between the left or right exterior curve of an arch and the rectangular framework surrounding it.

The space between two arches and a horizontal molding or cornice above them.

In architecture, the triangular space comprehended between the outer curve or extrados of an arch, a horizontal line drawn through its apex, and a vertical line through its springing; also, the wall-space between the outer moldings of two arches and a horizontal line or string-course above them, or between these outer moldings and the intrados of another arch rising above and inclosing the two.

The irregular triangular space between the curve of an arch and the inclosing right angle; or the space between the outer moldings of two contiguous arches and a horizontal line above them, or another arch above and inclosing them.

A narrow mat or passe partout for a picture.

The space (often triangular) between the outer curve of an arch (the extrados) and a straight-sided figure that bounds it; the space between two contiguous arches and a straight feature above them

The triangular space under a stair; the material that fills the space

A horizontal member between the windows of each storey of a tall building

An oriental rug having a pattern of arches; the design in the corners of such a rug, especially in a prayer rug

A phenotypic characteristic that evolved as a side effect of a true adaptation