0 used to refer to a group of people who are the first of several groups to do something, or to the first part of an activity that later happens again or is repeated after a pause:
Very few people alive today remember first-wave feminism, the movement of the 19th and early 20th centuries when the real groundwork was laid.
The role entailed recruiting a first-wave team, comprising a full-time member of staff responsible for the day-to-day running of the project, an assistant and a project audiologist.
Most of the first-wave EU members would enter the monetary union with high rates of unemployment.
