Source : Webster's Revised Unabridged Dictionary (1913)

Piano \Pi*a"no\, a. & adv. [It., even, smooth, soft, fr. L.
   planus even, level.] (Mus.)
   Soft; -- a direction to the performer to execute a certain
   passage softly, and with diminished volume of tone. (Abbrev.
   p.)

Piano \Pi*an"o\, Pianoforte \Pi*an"o*for`te\, n. [It. piano soft
   (fr. L. planus even, smooth; see {Plain}, a.) + It. forte
   strong, fr. L. fortis (see {Fort}).] (Mus.)
   A well-known musical instrument somewhat resembling the
   harpsichord, and consisting of a series of wires of graduated
   length, thickness, and tension, struck by hammers moved by
   keys.

   {Dumb piano}. See {Digitorium}.

   {Grand piano}. See under {Grand}.

   {Square piano}, one with a horizontal frame and an oblong
      case.

   {Upright piano}, one with an upright frame and vertical
      wires.

Source : WordNet®

piano
     adj : used chiefly as a direction or description in music; "the
           piano passages in the composition" [syn: {soft}] [ant:
           {forte}]

piano
     n 1: a stringed instrument that is played by depressing keys that
          cause hammers to strike tuned strings and produce sounds
          [syn: {pianoforte}, {forte-piano}]
     2: (music) low loudness [syn: {pianissimo}]

piano
     adv : used as a direction in music; to be played relatively softly
           [syn: {softly}] [ant: {forte}]