(1) Playing with "swing eighth notes"; (2) a form of syncopation, specifically off-beat accentuation, putting emphasis just before or after an expected beat, or emphasizing an unexpected beat; (3) a style of jazz popular in the 1930s and 1940s played by large dance bands; (4) a term of evaluation, as in "she swings."
Benny Goodman, "Swing, Swing, Swing" (1937)