r-version is not an official grammar term.
I came up with it to refer to the … well… r-versions of prefix verbs, like for example raufmachen, runterfallen, reingehen and so on.
Many prefix verbs have this r-version and its meaning is usually the most literal, “locational” take on the prefix verb.
“rausgehen” for example means to go outside, reinfallen means to fall inside and so on.
Many sources and teachers will say that it’s just a short, colloquial version of “her-“, and they make the students believe that rausgehen for example is really just an improper herausgehen.
But that kind of misses the reality of the language.
Many times, the r-version can be seen as short version of “dar-“, not “her-“.
And there are plenty of examples where there is an r-version and a her-version and they both have distinct meaning.
Not every r-version can be changed to a her-version and in my opinion they deserve to be seen as a distinct group, especially since they are unbelievably common.
In my series Prefix Verbs Explained you’ll see many r-versions and you’ll quickly get a feel for their meaning.