1) Unit of flow 2) Unit of flow 
Cusec is a measure of flow rate and is informal shorthand for `cubic feet per second` (28.317 litres per second). In the United States it is generally applied to water flow, particularly in rivers. Other informal synonyms are cfs and second-feet. (These are UK not US gallons: 1 imperial gallon = 1.201 US gallons) ...
unit of liquid flow equal to one cubic foot per second
a unit of flow of one cubic foot per second.