I think the blue moon is traditionally the third of four full moons in a quarter, and has just been simplified to the second full moon of the month. So, by popular usage of the last fifty years or so, the second full moon of a month is acceptable, but prior to that, it was the more complex definition.
I think there's a decent online reference about it...
Not the reference I remember, but here's something, anyway: http://britastro.org/computing/morsels_blue.html
Got twenty, afer reading the answers, strawberry and hay looked familiar. And how could I have missed first and last quarter. Didnt know the word gibbous though ( reminds me of gibbon.. while have to look up the etymology..) Didnt know atleast half of the months. I think allmost everyone will know harvest moon, atleast I think it is the best know name. Cool divers and educational :)
I think there's a decent online reference about it...
Not the reference I remember, but here's something, anyway: http://britastro.org/computing/morsels_blue.html