Yeah, it definitely isn't a standardized term. I've also been hearing "hard tech" but then got a feeling it has more and more been used for hardware projects, although I dont think that that was the original idea.
We actually never insisted on being called deep-tech, but we realised that was how others characterized us, especially when talking to investors (building a new programming language sounds pretty scary, although in our case it is a non turing complete DSL).
Fair enough. I was in a similar boat with my metaverse, pre-metaverse start-up https://ayvri.com - but a lot of what we were talking about was building 3D virtual worlds with AI. We didn't go looking for the deep tech label, but it was applied to us.
We actually never insisted on being called deep-tech, but we realised that was how others characterized us, especially when talking to investors (building a new programming language sounds pretty scary, although in our case it is a non turing complete DSL).