A crab apple is a small, sour apple that grows wild or on ornamental trees. Unlike the sweet apples you buy at the grocery store, crab apples are usually tart and bitter, making your mouth pucker if you bite into one raw. They're typically about the size of a cherry or golf ball, much smaller than regular apples.

Crab apple trees bloom with beautiful pink or white flowers in spring, which is why people often plant them in yards and parks for decoration. While the fruit is too sour to eat fresh, it's packed with pectin, a natural thickener, making crab apples perfect for making jelly, jam, or tart sauces. Some people also leave them on the tree for birds and other wildlife to eat during winter.

The term crab apple can also describe a grouchy, irritable person. If your neighbor complains about everything and snaps at kids playing outside, someone might call him a crab apple. This usage probably comes from the sour taste of the fruit: just as a crab apple makes your face scrunch up, a crabby person's attitude can be equally unpleasant.