The term "nightriders" typically refers to a group of people who operate at night in an unlawful or vigilante manner. However, there are several other synonyms that can be used to describe such a group. One common synonym is "night owls," which describes those who are active or work at night, but not necessarily in an illegal or vigilante capacity. The term "night stalkers" is also sometimes used to refer to people who engage in secretive or illicit activities at night. Other synonyms could include "night prowlers," "moonlight raiders," or "midnight marauders." Regardless of the term used, it is important to note that unlawful or vigilante actions should never be condoned or romanticized.