Ingress Protection Marking, classifies and rates the degree of protection

IPX - 4 splash resistance.

The IP Code, International Protection Marking, IEC standard 60529, sometimes interpreted as Ingress Protection Marking, classifies and rates the degree of protection provided against intrusion (body parts such as hands and fingers), dust, accidental contact, and water by mechanical casings and electrical enclosures. It is published by the International Electrotechnical Commission (IEC). The equivalent British standard is EN 60529.

 https://en.wikipedia.org/wiki/IP_Code