A network management function that is responsible for forwarding packets from a source to their destinations. Numerous algorithms exist that satisfy various network topologies and requirements to get data from point A to point B, or from point A to multiple point Bs.
It is the steps and actions involved in getting your data to and from everything2 which can be considered routing. First the data is routed around your brain to your muscles, muscles which activate some sort of input device. Your computer interprets the signals from the input device and formulates highly standardized requests which are send out of the first hop of your Internet connection. Along the way, further highly standardized steps are taken to classify, forward and distribute this information until it arrives here, at e2.
It is the steps of classification, forwarding, and distribution of information which forms a loose and general definition of the steps which involve routing.
As an exercise to the reader, consider how the actions of sending a letter via the USPS or navigating the highway system might be considered a routing function.