360-Degree Feedback Score is a measure of people performance through the eyes of other employees (both bosses and subordinates). It is a multi-item measure that could include measures of skill and capability, leadership, etc
This indicator is included in the book: Key Performance Indicators - the 75+ measures every manager needs to know, which contains an in-depth description of this KPI, as well as practical advice on data collection, calculations, target setting, and actual usage.