N-COUNT 志愿者;义务工作者;义工 A volunteer is someone who does work without being paid for it, because they want to do it.
N-COUNT 自告奋勇者;主动做事者 A volunteer is someone who offers to do a particular task or job without being forced to do it.
VERB 自告奋勇;主动要求 If you volunteer to do something, you offer to do it without being forced to do it.
VERB 主动提供（信息） If you volunteer information, you tell someone something without being asked.
N-COUNT 志愿兵;义勇军 A volunteer is someone who chooses to join the armed forces, especially during a war, as opposed to someone who is forced to join by law.
