1A series of eight notes, as the ordinary diatonic scale.
2A musical instrument having eight strings.
Mid 17th century. As adjective from classical Latin octōchordos having eight strings or notes (Vitruvius) and its etymon ancient Greek ὀκτάχορδος having eight strings or notes from ὀκτα- + χορδή; compare French octacorde, octocorde. As noun from post-classical Latin octachordum, octochordum musical instrument with eight strings from Hellenistic Greek ὀκτάχορδον series of eight notes, use as noun of neuter singular of ancient Greek ὀκτάχορδος; compare French octacorde eight-stringed lyre, octocorde eight-stringed instrument, scale with eight notes.