Biometric data are personal data that are collected using special methods, refer to physical, physiological or behavioural characteristics and make it possible to clearly identify a data subject. These include fingerprints, facial images, voice data or iris recognition images.
Article 4(14) GDPR (Definitions)
“biometric data” means personal data resulting from specific technical processing relating to the physical, physiological or behavioural characteristics of a natural person, which allow or confirm the unique identification of that natural person, such as facial images or dactyloscopic data;
Source: Regulation (EU) 2016/679