How does one define a Second Wave?

[lljkk]

So many people talking about this... but what does it mean to you - how would you know if we were in a second wave? Conversely, how would you know we had avoided a 2nd wave?

Is any increase in new cases relative to where we are now = 2nd wave?

[MRex]

Several are listed in this article, which appears factual, it's not certain to happen but it has happened with some other viruses:
www.cebm.net/covid-19/covid-19-epidemic-waves/.