- an expert on environmental problems.
- any person who advocates or works to protect the air, water, animals, plants, and other natural resources from pollution or its effects.
- a person who believes that differences between individuals or groups, especially in moral and intellectual attributes, are predominantly determined by environmental factors, as surroundings, upbringing, or experience (opposed to hereditarian).
- an adherent of environmentalism
- a person who is concerned with the maintenance of ecological balance and the conservation of the environment
- a person concerned with issues that affect the environment, such as pollution