"Regulation": 1. Law. Rule designed to carry out a specific piece of legislation. Usually enforced by a regulatory agency. 2. European Union law. An act of European Union (EU) law having direct effect in all member states. Regulations are passed either jointly by the EU Council and European Parliament, or by the EU Commission alone. 3. More generally, a rule to control, direct or manage an activity, organisation or system. It may or may not have legal authority.