Harmonica n. : A musical instrument, consisting of a series of hemispherical glasses which, by touching the edges with the dampened finger, give forth the tones.

Harmonica n. : A toy instrument of strips of glass or metal hung on two tapes, and struck with hammers.

Example:
What kind of Harmonica would be good for my dad?

Taxonomy
harmonica, reed, instrument, hole, plate, chromatic harmonica, chord, comb, the comb, octave, diatonic harmonica, harmonica players, Hohner, harp, tremolo harmonica, chromatic, tone, free reed.

Defination from the web:
harmonica is a free reed wind instrument which is played by blowing air into it or drawing air out by placing lips over individual holes ... The harmonica is used in blues and American folk music, jazz, classical music, country music, rock and roll, and pop music. ...