(1) The style of the ’30s, when the big band was the dominant form of jazz. The style implies certain types of harmony (use of added 6ths rather than 7ths in major and minor chords, of un-embellished diminished chords, frequent use of the augmented 5th and little use of the augmented 11th, etc.) and a rhythmic organization that states the beat explicitly, puts more weight on beats 1 and 3 and tends to obey the bar-line phrasing.
(2) A rhythmic manner, unique to jazz, in which the first of a pair of written 8th notes is played longer than the second, even twice as long, while the second tends to receive a slight accent, though the distribution of accents is irregular and syncopated. (The degree of this effect depends on the overall tempo, and is modified by the requirements of expression and phrasing.)