- any of various styles of jazz that have evolved since the early 1940s and are marked generally by harmonic and rhythmic complexity, emphasis on chord progressions rather than melody, a tendency to draw on classical forms and styles, and eclectic, allusive melodic tags in improvisation.
- any of the styles of jazz that evolved between the early 1940s and the later emergence of avant-garde jazz, characterized by a greater harmonic and rhythmic complexity than hitherto
