Embrace the ambiguity. People argue what it means for something to be a sandwich as well, and "tech debt" is just a tad more ambiguous. But as a metaphor and concept, it seems to be quite sticky and we've been talking about it for thirty years now, so I think people find it useful despite the ambiguity.

I recently explained tech debt to my 17 year old son, who is very interested in programming. It was difficult to come up with a crisp definition that captured what I mean by tech debt, but it was a good conversation.