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
