孤岛 literally means 'lonely island'—'孤' (gū) conveys isolation, solitude, or being cut off, while '岛' (dǎo) means 'island'. Together, they describe a physical island separated from the mainland or other landmasses by water. Geographically, it refers to islands with no direct land connection and often limited resources or accessibility.

Figuratively, 孤岛 is widely used as a metaphor for any isolated, self-contained, or neglected entity—such as a remote research station, a small community with little outside contact, or even a person feeling emotionally disconnected in a crowd. It carries a subtle connotation of vulnerability or resilience, depending on context, and appears frequently in literature, news reports about remote regions, and discussions of digital or social isolation.