A body of persons who have combined to execute a common purpose or advance a common cause; the whole organization which they form to effect their purpose; a society; e.g. the British Association for the Advancement of Science, the National Football Association, the Church Association, the Civil Service Supply Association.——牛津当代大辞典

an organization that consists of a group of people who have the same aims, do the same kind of work etc.——朗文当代大辞典  @en