A watchlist is a list of names a visitor management system screens arrivals against. If a check-in matches, the system alerts security rather than printing a badge, and the visitor is handled by a person instead of a tablet.
Uses are narrower than the name suggests. Most organisations use it for former employees subject to a restriction, individuals involved in a dispute, or names supplied by a corporate security team. Some regulated sites also screen against external sanctions lists.
Because a watchlist holds personal data about people who may never visit, it needs a clear owner, a review date, and a defined retention period.