Blanching is a cooking technique where a food item, usually a fruit or vegetable, is immersed in boiling water for a specified amount of time, removed from the boiling water and immediately submerged into iced water or placed under cold running water. The cold water is used to stop the food item from cooking.
For example, in our Garlic Cumin String Beans recipe, we place the string beans in boiling water for up to 4 minutes, then immediately submerge the hot string beans in iced cold water.
Learn more about blanching on this post on About.com.

String beans in boiling water. First step of blanching

String beans in iced water after boiling. Second step of blanching