OC'TAVE, a. [infra.] Denoting eight.
OC'TAVE, n. [L. octavus, eighth.]1. The eighth day after a festival.2. Eight days together after a festival.3. In music, an eighth, or an interval of seven degrees or twelve semitones. The octave is the most perfect of the chords, consisting of six full tones and two semitones major. It contains the whole diatonic scale.