A musical instrument that can be classified as both a percussion and string instrument. Has its roots in the middle ages, and many of the most famous songs ever written are either played solely upon this instrument, or feature it among others. Played by a skillful musician, it creates some of the most beautiful music in existence. Like almost all string instruments, it is difficult to learn to play well, and played incorrectly it is one of the most excruciating musical experiences available (although thankfully not as bad as a poorly played violin). Probably the most popular string instrument next to the guitar.
Playing guitar well gets you laid. Playing piano well (especially grand piano) gets you furious sex on top of it. And in every other room of your residence.
Undoubtedly the best instrument ever created by mankind. The piano is not only able to play soft and loud, but it can also play multiple parts simultaneously, making a single pianist the equivalent to an entire orchestra. The piano marks the pinnacle of human music technology, which is ironic (but should not be surprising) because it was invented in the 18th century.
Should not be confused with a keyboard, a piano-imitating instrument which has poorer quality sounds and wastes electricity, an insult to the piano. Obviously for these reasons it is used in rock bands.
And also the reason why I can't play in an orchestra (unless by invitation). They can't decide whether to put this damn thing into the strings or the percussion.