Underground railroad

An "underground railroad" is a network of secret routes, transports and safe places used to smuggle people out of the territory of a restrictive government. The term comes from the name of a similar network used on Earth in the 19th century United States, used to bring enslaved African descendants to Canada.

In the 2360s, an underground railroad was established to smuggle Romulan dissidents out of the Romulan Star Empire to the Federation. 

During the Dominion War, Thrax was a member of an underground railroad transporting Cardassians opposed to Dominion rule out of the Cardassian Union. (SS DS9 (Foundlings))

Following the collapse of the Romulan government in 2379, the Miridian system became a key underground railroad station for Remans escaping their enslavement.