Data breach and the GDPR
Security incidents are common. Perhaps someone leaves a secure door unlocked or a sensitive paper file exposed on their desk. Whether a security incident rises to the level of a data breach, however, is a legal question.
Under the GDPR, data breach is much broader term than under U.S. state data breach laws, for example.
Source: Top 10 Operational Responses to the GDPR Part 8: Data breach and the GDPR