An Environmentalist (medicine, social sciences) One who holds the view that environment, rather than heredity or culture, is the primary factor in the development of an individual or group. One who advocates for the protection of the biosphere from misuse from human activity through such measures as ecosystem protection, waste reduction and pollution prevention. Synonyms (one who advocates for the protection of the biosphere): greenie (chiefly Australia and New Zealand, slang, often derogatory), tree hugger (slang, often disapproving)