Black moon

Second new moon in a calendar month

Black moon is a name recently (2016) given to various new moons or absences of them, within a year. It is not a term used in astronomy and there is no single accepted definition of it. Among the meanings ascribed to it are these: a second new moon that appears in the same month; the third new moon in an astronomical season with four new moons; the absence of a new moon in February; or the absence of a full moon in February.

This keyword could refer to multiple things. Here are some suggestions: