Common-use word for Government licenced 'Radio Amatuer Operator'. Often thought to be a CB operator, but with much more technical knowledge and apparatus for world-wide communication. Some "hams" are quite content to 'work around the corner' with very simple equipment, whilst others use earth-moon-earth and satellites to communicate with each other. Many Governments register 'radio-hams' as emergency telecoms stations in the event of national disasters etc.
Boy- "Hey mister, are you a CBer?"
Elmer - "No, I'm a Radio-Ham - a bit like a CBer's big brother, but much more complicated"