organ -- (a fully differentiated structural and functional unit in an animal that is specialized for some particular function)
organ -- (a government agency or instrument devoted to the performance of some specific function; "The Census Bureau is an organ of the Commerce Department")
organ -- (a periodical that is published by a special interest group; "the organ of the communist party")
organ, pipe organ -- (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)
harmonium, organ, reed organ -- (a free-reed instrument in which air is forced through the reeds by bellows)