Quarter Moon
When you pick at your toe nails when they are long enough to get a peice that looks like a quarter moon.
While I was on the computer, I picked quarter moons til they were all gone.
Black Moon Quarter
A span of 3 months in which 4 new moons occur.
Between October 1st and December 31st there were 4 new moons instead of the usual 3 making those 3 months a black moon quarter (as in a quarter of a year).