(historical, music) A type of reed organ with a single keyboard. / (music) An accordion where the melody-side keyboard is limited to the notes of diatonic scales in a small number of keys.

(historical, US) A music hall.

plural of melodeon

(Ireland, informal) terrible, appalling; of very poor quality / (Ireland, informal) cacophonous; raucous

plural of melodeonist

Someone who plays a melodeon.