The term is used for the descendants of Kal-El, the original Superman, who continue to uphold his legacy of heroism well into the 853rd century, as depicted in the DC One Million crossover.
In the future timeline of DC One Million, the death of Lois Lane compels Superman to leave Earth and wander the universe alone at the end of the 21st century.
Their powers are increased significantly again at the dawn of the 700th century, when the original Superman finally returns from his wandering, takes up residence on Earth's sun, and enters into a pact with the Superman of that time to provide them access to the vast powers he had gained in the 68,000 years he had been gone, in return for the dynasty's vow to continue to protect Earth.
The ongoing Rebirth storyline raises new important questions about the Superman Dynasty future timeline.
Both versions have recently been merged into a combined Superman and Lois Lane, whose new history seems to mirror the pre-Flashpoint continuity far more than that of the New 52.