Definition of the data subject means any freely given, specific, informed and unambiguous indication of the datasubject’s wishes by which he or she, by a statement or by a clear affirmative action, signifies agreement to the processing of personal data relating to him or her
Source
Point (11) of Article 4 of Regulation (EU) 2016/679 of the European Parliament and of the Council of 27 April 2016
Link
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32016R0679