Noun
a long time
Source: WordNetOnce in a blue moon someone like you comes along. Van Morrison
Magic doesn't happen often - not once in a blue moon ... I expect there isn't another magic ship like this one in the whole world. Hilda Lewis
Another thing that I don't like to do is show too much how it goes. I do it once in a blue moon. Sometimes there are lessons when I don't pick up a violin at all. Itzhak Perlman
Once in a blue moon a captain imposes his influence not just upon his opponents, but on a generation of cricketers, by the sheer force of his personality. James Coldham
When I made Blue Moon Swamp, there was a lot of trial and error; I was trying to find people who would be simpatico with my style, and with what I had in mind for the album. John Fogerty
something that happens once in blue moon almost never happens Source: Internet