[lispm]

> I know some people have long used "DSL" in this way, especially among LISP fans

generally this would be called an "embedded domain specific language". Some languages are relatively flexible to change the syntax. For example Common Lisp has reader macros to change the token syntax and macros to change the Lisp syntax. With that one can create all kinds of embedded languages, incl. domain specific languages (languages which are specific to a special domain). Examples would be embedded logic languages, query languages, rule based languages, languages to describe user interfaces, etc. The Common Lisp standard has a notorious example for that, a complex LOOP construct, which uses a very different syntax: https://www.lispworks.com/documentation/HyperSpec/Body/m_loo...

There are other real-world examples out there, for example an embedded domain specific language to describe 3d objects in the domain of parametric CAD, for description of technical things like turbines or other parts of an aircraft.