Merriam-Webster's Collegiate® Dictionary, 11th Edition
PIANO
I. adverb or adjective see: floor
Date: 1683
at a soft volume ; soft ,
II. noun (plural pianos)
Etymology: Italian, short for pianoforte, from gravicembalo col piano 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