Any tree of genus Malus which does not grow apples.  Now does
that make any sense? Well, it turns out that the only
distinction between apples and crabapples is the size of the
fruit - if they're greater than 2 inches in diameter, they're
apples and the tree they're growing on is an apple tree. If
they're that size or smaller, they're crabapples and the tree is
a crabapple tree. There is no deeper meaning behind the
distinction.  Being that small, crabapples aren't often eaten,
although they can be made into jelly (and perhaps even wine if
you're good at that sort of thing). The fruit are very sour and
often referred to as "crab apples," unlike the tree which is
usually written as a single word.  Crabapple trees are most
often not grown for their fruit. Malus is part of family
Rosaceae - the roses - and the trees are typically grown for
ornamental purposes, producing colorful flowers. Most of those
that have been bred specifically for their flowers have small
fruit, often less than an inch in diameter and ref