I am not a fan of this buzzword (and indeed buzzwords in general, the comment above was intending to make fun of HSBC IT for even failing at the buzzword game), but the notion of NewSQL was roughly to keep the relational model and consistency guarantees of traditional SQL databases, but also have horizontal scalability in line with NoSQL databases. DBs like VoltDB and Spanner come to mind as examples -- here are two relevant blog posts from those teams:
VoltDB: https://www.voltdb.com/blog/2016/09/nosql-vs-newsql-whats-di...
Spanner: https://cloud.google.com/blog/products/gcp/from-nosql-to-new...