A turnip is a slightly bitter-flavored root vegetable. In Japan, it's common to pickle turnips and serve them as a cold snack or in a stir fry with other vegetables.
You can recognize a turnip by its roundish shape and its white color, often accented at the top by pink or purple. Turnips also have green leaves that can be cooked and eaten. Some people also call rutabagas turnips, although these are actually a cross between a turnip and cabbage. Experts think the turn part of turnip stems from the idea that it looks like it's been turned, or rotated and shaped, on a lathe.