From Longman Dictionary of Contemporary Englishmouth organˈmouth ˌorgan noun [countable] APMa small musical instrument that you play by blowing or sucking and moving it from side to side near your mouth SYN harmonica
Examples from the Corpus
mouth organ• It sounded like a mouth organ.• I mean, you get people who blow a couple of bars on a mouth organ and then hold out their hands.• He played first a whistle, then a mouth organ, then a trumpet.• I gave her a ridiculously expensive mouth organ one Christmas, much like a cocktail cabinet.• Adler gave the instrument dignity, inspiring composers such as Vaughan Williams and Joaquin Rodrigo to write for the humble mouth organ.• I don't remember the clothes you wore, or your beautiful hair, or the sardines, or the mouth organ. 