A topolect is regional speech that is not considered its own language or dialect.

It comes from the Chinese translation of 方言 (fāngyán), and is used when it would be too controversial to declare something a language (or dialect).

SOURCE First came across it in The Three Body Problem.

https://en.wiktionary.org/wiki/topolect http://languagelog.ldc.upenn.edu/nll/?p=2423 https://en.wikipedia.org/wiki/Fangyan