Crab Apples

defined not by taste, color, season or genetic marker a crab apple is any apple with a diameter of under 2 inches. It is one of the simplest segregations devised by man in pomology. No subjectivity, no feasance, no deliberation. It is sacrosanct in a universe of few such things.

http://www.dawesarb.org/pdf/collectionsgardens/best-crab-apples.pdf