1. One file transmission in a series required to get a file from point A to point B on a store-and-forward network. On such networks (including UUCPNET and FidoNet), an important inter-machine metric is the number of hops in the shortest path between them, which can be more significant than their geographical separation. See bang path.
2. To log in to a remote machine, especially via rlogin or telnet. "I'll hop over to foovax to FTP that."