Because the term is not scientific, much like Blood Moon or Blue Moon, there is no consensus as to what exactly it means.
By one definition, a Black Moon is the second of two New Moons in the same calendar month.
A similar definition can be applied to the Blue Moon – the second of two Full Moons in one calendar month.
The terms is also sometimes used in a month when no New Moons appear.
This is a rare occurrence that only happens in February, every five to 10 years.