Can be used in a variety of contexts, most often to express dissatisfaction, or that you think whatever you're talking about is silly or stupid. Can also be used mid-sentence, for example "I gammon told her that she is a frog" or "I was just gammoning!" indicate that what was said, was said in a joking manner. In wide use in the Northern Territory of Australia.
Definitions include: Usually means automatically or concurrently complete one action without stopping the first action, i.e. on the fly online Help means that you don't have to stop using a software program in order to use the online Help.