green belt

Short definition from Wiktionary

Noun

1. 1
   Senses relating to an area of land with plants on it: A strip of land with plants in a place which is otherwise bare.
2. 2
   Senses relating to an area of land with plants on it: A strip of land on which trees are planted to protect against desertification, soil erosion, etc.
3. 3
   Senses relating to an area of land with plants on it: A strip of land next to a building, open space, road, etc., with plants on it, intended for exercise or recreation.
4. 4
   Senses relating to an area of land with plants on it: An area of agricultural land around an urban area that is protected from large-scale building.
5. 5
   A belt which is green in colour worn by a person who has achieved a certain (usually intermediate) level of skill in a martial art, especially judo or karate; also, the level of skill represented by this belt.
6. 6
   A person who has earned the rank of green belt in a martial art.