Knob celery is a type of celery with a large, round stem at the base. It is also known by several other names such as celeriac, turnip-rooted celery, and celery root. The word "knob" refers to the rounded shape of the celery stem and is often used as a synonym for celeriac. However, there are other synonyms that can be used to describe this vegetable, including root celery, celery knob, and turnip-rooted celery. Despite its ugly appearance, knob celery is a nutrient-rich vegetable that is commonly used in soups, stews, and salads to add flavor and texture. It has a slightly nutty taste and can be cooked in various ways to enhance its flavor.