polychord

from The Century Dictionary.

• Having many chords or strings.
• noun A musical instrument invented by F. Hillmer in 1799, but never generally used.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Having many strings.
• noun A musical instrument of ten strings.
• noun An apparatus for coupling two octave notes, capable of being attached to a keyed instrument.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun music Two or more chords, each constructed in a different manner, one on top of the other, multiple chords
• noun music a musical instrument having ten strings
• noun music a device, attached to a keyboard, for coupling two octave notes
• adjective music having many strings