Used often in contexts related to technology, especially when referring to robotic systems or automated processes. The factory uses an unmanned assembly line for packaging.
Pro Tip 2/3
Not Science Fiction
Even though it sounds futuristic, 'unmanned' refers to real, current technology, not to science fiction gadgets. Unmanned spacecraft are exploring the surface of Mars right now.
Pro Tip 3/3
Safety and Risk
Implies safety or risk management by removing humans from dangerous roles or environments. Unmanned robots are used to defuse explosive devices.