ˈɔɹ.ɡən ˈɔː.ɡən (music) an electronic simulation of a pipe organ a free-reeded instrument with a piano keyboard in which air is forced through the reeds by bellows wind instrument whose sound is produced by means of pipes arranged in sets supplied with air from a bellows and controlled from a large complex musical keyboard a fully differentiated structural and functional unit in an animal that is specialized for some particular function a periodical that is published by a special interest group the organ of the communist party a government agency or instrument devoted to the performance of some specific function The Census Bureau is an organ of the Commerce Department