What does "mouth organ" mean?

A free reed aerophone, in the Western tradition commonly the harmonica.

What is a synonym for "mouth organ"?

Common synonyms include: harmonica, harmonicas, harp, mouth harp.

Pronounced //maʊθ ˈoɹɡən//.

/maʊθ ˈoɹɡən/ noun

noun ·Rare ·Advanced level

Noun

1
A free reed aerophone, in the Western tradition commonly the harmonica.
2
a small rectangular free-reed instrument having a row of free reeds set back in air holes and played by blowing into the desired hole wordnet

From mouth + organ.