Definition
Means any operation or set of operations which is performed on personal data or on sets of personal
data, whether or not by automated means, such as collection, recording, organisation, structuring, storage, adaptation or alteration, retrieval, consultation, use, disclosure by transmission, dissemination or otherwise making available, alignment or combination, restriction, erasure or destruction
Source
Point (2) 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