spandrel

• spandril

From a diminutive of Anglo-Norman spaundre, of uncertain origin, perhaps from Old French espandre (“to expand, extend, spread”). In the biology sense first used by Stephen Jay Gould and Richard Lewontin.[1]

spandrel (plural spandrels)

1. (architecture) 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.

   Coordinate term: pendentive

2. (evolutionary theory) A phenotypic characteristic that evolved as a side effect of a true adaptation.
   • 2009, Anna R. Kinsella, Language Evolution and Syntactic Theory, Cambridge University Press (ISBN 9780521895309), page 13:

     Another type of theory emphasises the sometimes accidental nature of evolution. A spandrel is a structure arising as a by-product of some other architectural configuration. In evolutionary terms, a spandrel is some trait of an organism which emerges not through direct adaptionist or exaptationist means, but rather as a side effect of some other evolutionary development.

3. (architecture) The triangular space under a stair; the material that fills the space.
4. (architecture) A horizontal member between the windows of each storey of a tall building.
5. An oriental rug having a pattern of arches; the design in the corners of such a rug, especially in a prayer rug.

• spandrelled

• exaptation

• spandrel on Wikipedia.Wikipedia
• spandrel (biology) on Wikipedia.Wikipedia