Make sure you're sitting down for this one, Shmoopers: Jazz is called Jazz because it's structured on a little musical form called… jazz.
This is a novel that has alternating character voices that act like solos, repeating refrains that keep it flowing in one general direction, a feeling of dissonance and harmony at the same dang time—all of which are attributes of a musical form called jazz. Basically, Morrison set out to write a book whose structure mimicked the musical structure of jazz. Ambitious much, Morrison? Good thing she has the immense literary talent to pull it off.