Final answer:
"Underground" in the context of resistance or rebellion refers to covert and suppressed efforts against dominant authorities. The term is symbolic, describing secretive operations like the Underground Railroad during slavery in the US or resistance movements during the Holocaust, not literal underground activities.
Step-by-step explanation:
"Underground" typically refers to clandestine, secret actions and organizations that operate in stealth to resist or rebel against authority or oppressive systems. This term can describe various activities and networks that provide support to those in defiance of established powers. For instance, the Underground Railroad was a network of secret routes and safe houses that helped escaped slaves in the United States reach freedom in the 19th century. This network wasn't literally underground nor a railroad but used the term to reflect its covert nature and the terminology of railways for its operation.
During World War II, underground resistance movements also formed in ghettos and occupied countries to oppose Nazi Germany. These movements conducted a range of activities from escaping and hiding, to armed uprisings, as well as cultural and spiritual preservation.
Underground economies also relate to this concept, referring to the unregulated exchange of goods and services that exist outside of governmental oversight. Although distinct from the resistance networks, these economies can underscore a form of resistance to the established economic system by operating independently.