Definition: A cubic kilometer per second (km3/s) is a unit of volumetric flow rate representing one cubic kilometer of substance passing a point in one second. It is used to measure extremely large volumes of fluid or gas flow.

History/origin: The unit combines the cubic kilometer, a very large unit of volume, with 'per second,' indicating an extremely high rate of flow. It's primarily used in geological or astrophysical contexts where vast quantities are involved.

Current use: Km3/s is used in fields such as astrophysics (e.g., measuring material ejected from celestial events), geology (e.g., estimating the volume of volcanic eruptions), and extremely large scale fluid dynamic modeling.