1. noun
A keyboard musical instrument, usually ranging over seven octaves, with white and black keys, played by pressing these keys, causing hammers to strike strings.
2. adjective
Soft. Used as a directive in in its abbreviated form, p., to indicate lowering the volume of the music. In the pianoforte this is done by pressing the instruments keys more lightly.
See Also: mezzo piano, mp, pianissimo, pp
Wikipedia foundation.