A crock is a sturdy container made from clay that has been hardened by baking it at high temperatures, a process called firing. For thousands of years, people stored food in crocks: pickles, sauerkraut, butter, salted meat, and other provisions that needed to stay fresh. The thick ceramic walls kept contents cool and protected them from insects and rodents. Many families kept a butter crock in their pantry or a pickle crock in their cellar.

Crocks usually have a simple, cylindrical shape with thick walls and often a wide mouth at the top. Some have lids, others don't. Today, we still use crocks for making fermented foods like kimchi or for keeping sourdough starter, and people collect antique crocks decorated with blue designs.

The word also appears in informal expressions. When someone says “that's a crock” or “what a crock,” they mean something is nonsense or completely untrue. If your friend claims they can run faster than a cheetah, you might say, “that's a crock!”