At least one Eurostat publication uses the following def of recession:
A recession is normally defined in terms of zero or negative growth of GDP in at least two successive quarters.
And they cite a whole bunch of EU regs at the end on data collection and terminology. Which unfortunately, by their sizeable number, make it difficult to quickly tell if recession is defined in one of those EU regs or if Eurostat is just using a textbook definition. So, do EU regulations define the term "recession" (at least for Eurostat's purposes)?