From WordNet (r) 2.0 (August 2003) [wn]:
greenhouse
adj : of or relating to or caused by the greenhouse effect;
"greehouse gases"
n : a building with glass walls and roof; for the cultivation
and exhibition of plants under controlled conditions
[syn: 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]