As a Noun:
1. A person who offers to do something without being obliged or forced to do so, especially socially useful work for which they are not paid. English = volunteer.
2. Someone who chooses to join the army, navy, or air force, especially in wartime, as opposed to being forced to join by law. English = volunteer.
3. Someone who has been chosen to talk or act on behalf of another person or a group of people and to express their views. English = representative.
4. A person in a meeting who formally support a motion. English = seconder.
As a Verb or Adjective:
1. To offer to do something, rather than being forced to do it, especially socially useful work for which you are not paid. English = volunteer.
2. To choose to join the army, navy, or air force, especially in wartime, as opposed to being forced to join by law. English = volunteer.
3. To talk or act on behalf of another person or group of people and to express their views. English = represent.
4. In meetings, to volunteer by putting up your hand to support a motion. English = second.