Akademik

a flattened third or seventh

1. : a minor interval (at the third and seventh degree) occurring in a melody or harmony where a major would be expected

2. : a wrong, off-pitch, or badly sounded note

a flatted note, esp. the third or the seventh degree of the scale, recurring frequently in blues and jazz as a characteristic feature.

[1925-30]

blue note noun

A flattened note, usu third or seventh, characteristic of the blues

Main Entry: ↑blue

blue note,

a note between the usual notes in jazz, especially a third or seventh note played or sung a quarter or a half tone flat, characteristic of the blues.

n. Music a minor interval where a major would be expected, used esp. in jazz

ˈblue note 7 [blue note] noun (music)

a note which is slightly lower than the third, fifth or seventh note of the ↑scale, often used in ↑jazz