What does JAR stand for?

Justice Acquisition Regulations

Justice Acquisition Regulation

Japanese Association of Refrigeratjon

Jardine Math.sr

Jason Andrew Relva

Java Archive (compressed JAVA class files)

Just Another Rifle

Java archive file

Jar Syndrome: Just Ain't Right (often Used When A Patient Has Multiple Issues)

Joint Aviation Regulations (European FAR) 

Were a set of common comprehensive and detailed aviation requirement issued by the Joint Aviation Authorities, intended to minimise Type Certification problems on joint ventures, and also to facilitate the export and import of aviation products.