Glossary
Starting flow
The lowest flow at which a meter's register begins to move. It is a commonly quoted figure but is not one of the flow rates defined in ISO 4064, and at that flow the meter's error can be large.
Why it matters
Starting flow shows whether very small leaks and drips register at all, but it is not a measure of accuracy. Compare meters on Q1 and the R ratio first.
Source
General usage