Real Dictionary

greenhouse effect
singular noun: The greenhouse effect is the problem caused by increased quantities of gases such as carbon dioxide in the air. These gases trap the heat from the sun, and cause a gradual rise in the temperature of the Earth's atmosphere.

greenhouse effect in American English
the warming of a planet's surface and lower atmosphere caused by trapped solar radiation: solar shortwave radiation penetrates to the planet's surface and is reradiated into the atmosphere as infrared waves that are then absorbed by carbon dioxide, water
noun: an atmospheric heating phenomenon, caused by short-wave solar radiation being readily transmitted inward through the earth's atmosphere but longer-wavelength heat radiation less readily transmitted outward, owing to its absorption by atmospheric carbon di

greenhouse effect in British English
noun: an effect occurring in greenhouses, etc, in which radiant heat from the sun passes through the glass warming the contents, the radiant heat from inside being trapped by the glass