Syncopation is a
rhythm that exists just before or just after the meter count. The dictionary defines syncopate as: "...change a regular rhythm by beginning a note on an unaccented beat and holding it into an accented one or beginning it midway through a beat and continuing it midway into the next one".
Syncopation is used on occasion in many music styles, including classical music, but is is a fundamental constant presence in such styles as ragtime and jazz.