Definition of "Organ" :

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

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

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

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

noun: a periodical that is published by a special interest group

"The organ of the communist party."

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

"The Census Bureau is an organ of the Commerce Department."