Short for superuser do (or substitute user do, depending on who you ask), it allows users to. For some reason, much police dispatch traffic is both unencrypted and unencoded. While encoded transmissions share the digital signature of a waterfall, looking like a strip of digital.
Anyone who has used linux long enough is familiar with sudo. Once this is done, you can easily find analog voice transmissions to listen in on. And we meet again crackers!