A "reverse bathtub" refers to a specific bathtub design by Cesana that features a minimalist, striking style with a unique shower bathscreen made of two independent doors. This design allows the tub to be used both as a bathtub and a shower enclosure. The shower doors swing independently, with one smaller door opening inward for easy access to shower controls without getting wet, and another larger door opening both ways. The tub also includes practical features like a towel rail on the shower door handle and a sliding teak shelf/seat that can be used for sitting or as a shelf for toiletries. It is reinforced with an aluminum frame and can include water massage systems. This design is noted for being easy to clean and maintain and fits well with various architectural styles.

Additionally, the term "reverse bathtub" has also appeared in a different, less formal context related to building construction to describe a seal or design element that keeps water out of basements or lower floors, but this is not the common or primary meaning.

The primary understanding relates to the bathtub design described above.