The prefix “nano-”, used in scientific terminology to denote a factor of one-billionth (10⁻⁹). In metric units, nano is the prefix that turns a meter into a nanometer.
A very small object, device, or entity, especially one created or manipulated through nanotechnology. Engineers are testing nanos that can deliver medicine directly to cancer cells.
Informal: the field or study of nanotechnology. He’s doing his doctorate in nano at the university’s materials lab.