spandrel

Meanings

1. The space (often more or less 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.
2. Horizontal member between the windows of successive storeys of a tall building.
3. The triangular space under a stair; the material that fills the space.
4. An oriental rug having a pattern of arches; the design in the corners of such a rug, especially in a prayer rug.
5. A phenotypic characteristic that evolved as a side effect of an adaptation in response to evolutionary pressure.
6. soffit (usually used to describe metal or corrugated plastic types of roof soffit)

Etymology

From a diminutive in -el of Anglo-Norman spaundre, of uncertain origin, perhaps from Old French espandre (“to expand, extend, spread”). More at spawn, expand. In the field of biology first used by Stephen Jay Gould and Richard Lewontin.