From WordNet (r) 3.0 (2006) [wn]:
greenhouse
adj 1: of or relating to or caused by the greenhouse effect;
"greenhouse gases"
n 1: a building with glass walls and roof; for the cultivation
and exhibition of plants under controlled conditions [syn:
greenhouse, nursery, glasshouse]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Greenhouse \Green"house`\, n.
A house in which tender plants are cultivated and sheltered
from the weather.
[1913 Webster]