A tub is a large, open container, typically round or oval, used for holding water or other liquids. The most familiar kind is a bathtub, where you sit to wash yourself. Before indoor plumbing became common, people bathed in wooden or metal tubs that had to be filled with water heated on the stove and carried bucket by bucket.

The word describes other containers too. Farmers might store grain or feed animals from wooden tubs. A tub of ice cream sits in your freezer. Butter comes in small plastic tubs. Laundry tubs hold water for washing clothes. What makes something a tub rather than a bowl or bucket is usually its size and width: tubs are broad and deep, made for holding a substantial amount of something.

Sometimes people use tub playfully to describe old, slow boats. A ship that moves sluggishly through the water might be called an old tub, suggesting it's clumsy and past its prime. The comparison works because both boats and bathtubs are hollow vessels that hold water, though one sits in the water rather than being filled with it.