Interactive audio is the term used to refer to audio technology that's made specifically to create sound through interaction.
One might argue that is simply called a "music instrument".
"Interactive audio" isn't new at all. It used to simply be called MIDI, synthesis, electronic instrumentation or just "programming" audio. What is new is the imagery associated with tablets, cell phones and the reinvention of the MIDI ideal through protocols like OSC. This coupled with the fact that low level programming is much more easily learned and omnipresent due to the internet. I think all these factors collectively have allowed a marketing shift. If you ask someone what MIDI is they'll look at your with a blank stare, but if you say interactive audio they might, through inductive reasoning get some kind of idea in their head with minimal effort.
Reminds me of the phrase "Controllerism" being used by self marketing club DJ's to describe sending MIDI messages to a sound module as if it is something "new" or "innovative" and divorced from a spec that was created 30 years ago.