Step 1: Recall why Zero FIR was introduced.
It was brought in so that jurisdiction would not stop a victim from getting their complaint registered without delay.
Step 2: Eliminate the wrong descriptions.
It is not limited to metropolitan cities or cybercrime cases, and it does still get a serial number once transferred, it is only recorded as zero at the first station.
Step 3: State the correct meaning.
A Zero FIR can be registered at any police station regardless of where the offence took place, and is later transferred to the police station that actually has jurisdiction.
\[ \boxed{\text{An FIR that can be registered at any police station irrespective of jurisdiction}} \]