Merriam-Webster Collegiate Dictionary - piano

 I. adverb or adjective  Etymology: Italian, from Late Latin planus smooth, from Latin, level — more at floor  Date: 1683 at a soft volume ; soft — used as a direction in music  II. noun  (plural ~s)  Etymology: Italian, short for ~forte, from gravicembalo col ~ e forte, literally, harpsichord with soft and loud; from the fact that its tones could be varied in loudness  Date: 1803 a musical instrument having steel wire strings that sound when struck by felt-covered hammers operated from a keyboard