Oc"tave (?), n. [F., fr. L. octava an eighth, fr. octavus eighth, fr. octo eight. See Eight, and cf. Octavo, Utas.]
1. The eighth day after a church festival, the festival day being included; also, the week following a church festival. The octaves of Easter." Jer. Taylor.
2. (Mus.) (a) The eighth tone in the scale; the interval between one and eight of the scale, or any interval of equal length; an interval of five tones and two semitones. (b) The whole diatonic scale itself.