What is a large plumbing fixture primarily used for bathing called?

The term for a large plumbing fixture primarily used for bathing is indeed a bathtub. A bathtub is designed specifically to hold water so that individuals can immerse themselves while taking a bath, providing a space for relaxing and cleaning. Typically, bathtubs can be built into a bathroom structure or can be standalone units, and they often feature various designs, sizes, and materials to accommodate different tastes and needs.

In contrast, showers are primarily used for standing bathing and usually involve water flowing from a showerhead above, which is more about rinsing than immersing oneself in water. A spa generally refers to a larger water environment designed for relaxation and therapeutic purposes, often containing features beyond just a bathtub, such as jets and seating areas. A washbasin, also known as a sink, is intended for washing hands and faces, not for bathing purposes. Thus, the bathtub is the correct identification for a large plumbing fixture dedicated to bathing.