"RAR" is a product line for Abaco Systems , featuring avionics databus interfaces like the RAR-cPCI or RAR-EC , which support ARINC protocols.
It could refer to a specific node or file path on a corporate website, such as a BioCryst Pharmaceuticals SEC filing hosted at node ID 23706. 23706.rar
However, the term could also be interpreted in a few other ways: "RAR" is a product line for Abaco Systems