The Seven Galaxies were a collection of galaxies. The Kaleds believed that Skaro was the only planet capable of supporting live in all of the Seven Galaxies. (TV: Genesis of the Daleks)
They were used in a question by the Eighth Doctor, "Why in the Seven Galaxies..." (AUDIO: Neverland) and by Romana II, "What in the Seven Galaxies?" (AUDIO: Zagreus)