greenhouse UK /ˈɡɹiːnhaʊs/US /ˈɡɹːnˌ(h)aʊs/noun 5verb 2forms 3 noun5 •A building used to grow plants, particularly one with large glass windows or plastic sheeting to trap heat from sunlight even in intemperate seasons or climates. •A hot state in global climate. •(slang, old-fashioned) The glass of a plane's cockpit.In the slang of the Royal Air Force man, the cockpit of his plane is the ‘pulpit’ or ‘office’, the glass covering over it the ‘greenhouse’. — 1941 •A structure that shields the operating table to protect against bacteria.Figure 2.6 shows the diagram Charnley published of the airflow in the 'greenhouse'; it can be seen that reasonable downward unidirectional airflow was achieved close to the operating table. — 2010 •(Ireland, slang) A public toilet.All kinds of places are good for ads. That quack doctor for the clap used to be stuck up in all the greenhouses. — 1922 verb2 •To place (plants) in a greenhouse. •(figurative) To nurture in order to promote growth.It's almost impossible to make judgements when you're being playful – as by definition it's spontaneous activity – so your baby ideas get nurtured and greenhoused better. — 2008 formsgreenhoused · greenhousing · greenhouses