How do you spell Hothouse

Available Definitions:
1)  n. - A house kept warm to shelter tender plants and shrubs from the cold air; a place in which the plants of warmer climates may be reared, and fruits ripened.
2)  n. - A bagnio, or bathing house.
3)  n. - A brothel; a bagnio.
4)  n. - A heated room for drying green ware.