Definition (noun): a fully differentiated structural and functional unit in an animal that is specialized for some particular function

Definition (noun): a government agency or instrument devoted to the performance of some specific function

Example: The Census Bureau is an organ of the Commerce Department

Definition (noun): (music) an electronic simulation of a pipe organ

Definition (noun): a periodical that is published by a special interest group

Example: the organ of the communist party

Definition (noun): 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

Definition (noun): a free-reeded instrument with a piano keyboard in which air is forced through the reeds by bellows