I am developing this concept in a paper for a media journal. It derives from research at the Olympic Games and my present definition is as follows:

 a phenomenon which involves infiltrating the privileged position of traditional media organizations either within a fixed media event or through new media platforms and, usually, via a combination of the two, by the citizen-non-journalist. Ambush media is constituted by three key processes: a) piggyjacking on the intellectual property of traditional media to generate competing attention, b) reversing the direction of interrogation towards traditional media and then broadcasting the results, often before traditional media and c) infiltrating physical environments that have been traditionally reserved for traditional media.

More to come!