Definition of octave
1
:an 8-day period of observances beginning with a festival day
2 a
:a stanza of eight lines :ottava rima
b
:the first eight lines of an Italian sonnet
3 a
:a musical interval embracing eight diatonic degrees
b
:a tone or note at this interval
c
:the harmonic combination of two tones an octave apart
d
:the whole series of notes, tones, or digitals comprised within this interval and forming the unit of the modern scale
e
:an organ stop giving tones an octave above those corresponding to the keys
4
:the interval between two frequencies (as in an electromagnetic spectrum) having a ratio of 2 to 1
5
:a group of eight
