1. To plunge food (usually vegetables and fruits) into boiling water briefly, then into cold water to stop the cooking process. Blanching is used to firm the flesh, to loosen skins (as with peaches and tomatoes) and to heighten and set color and flavor (as with vegetables before freezing). See also parboil. 2. This term also refers to the horticultural technique whereby the leaves of plants are whitened or prevented from becoming green by growing them in complete darkness. It's this labor-intensive process that makes Belgian endive so expensive.