Definition of keyboard instrument:
(n) :
(music) Any musical instrument which features a keyboard, such as a piano, synthesizer or celesta.
(n) :
(music) Any musical instrument that produces sound directly from the manipulation of a keyboard by the performer, including a piano and a celesta.
(n) :
(music) Any musical instrument (a chordophone) that uses a keyboard to manipulate strings which produce sound, including a piano.