From Wiktionary, the free dictionary
From tub + shower.
tub-shower (plural tub-showers)
- An installation found in bathrooms, consisting of a stall that has a bathtub as the basin base with a bath shower atop it.
2004, Roger German, Remodeling a Basement, page 82:Plumbing a tub-shower is more complicated than plumbing a sink.
