green roof

Short definition from Wiktionary

Noun

1. 1
   A roof of a house or other building which is covered with soil and grass, plants, trees, or other landscaping materials.
2. 2
   A roof of a house or other building on which solar panels, solar hot water collectors, wind powered turbines, or other natural energy collectors are placed.
3. 3
   A roof of a house or other building which is designed to collect rainfall for use in gardens, lawns, or as drinking water.