Ockmenic 9 phasing into another dimension
A Brigadoon-type planet was a planet that alternated its existence between two different dimensions. (LD: "The Stars At Night")
Meridian shifted into normal space-time for a length of days once every sixty years. (DS9: "Meridian")
Ockmenic 9 phased into normal space for two hours per year. (LD: "The Stars At Night")
The term is a reference to the musical Brigadoon, set in a Scottish village that appears for one day per century.