That is a standard clinical term for the some of the manifestations of tardive dyskinesia as regards aspects of it such as tardive dystonia that create motor rigidity. A person's face is tight because of this and it resembles a mask. This term was first used somewhat after the invention of Thorazine (when higher doses of antipsychotics were used and there was less of an understanding of side effects both short term and long term of antipsychotics) because the idea of medications creating Parkinsonism had not occured before) There are many clinical terms for the various types of extra pyramidal side effects and aspects of tardive and this specific one means that if a person encounters that it may be tardive dyskinesia. This occurs with me when various treatments for tardive run out. I can see it for myself. The basic common sense rule is to report any changes in motion to your psychiatrist and they would do a movement disorders test which they should do regularly regardless. Also not also extreme movement changes are necessarily tardive dyskinesia. Dystonia (which is a temporary movement disorder) when untreated can become dangerous so generally psychiatrists give a person a side effect pill at a maintenance dose and even before I acquired tardive I (with the permission of my psychiatrist) carried chewable Benadryl with me in case I would encounter anything like this but that would be within a psychiatrist's discretion.
Thanks, that was really informative and helpful because now I know what to watch for instead of just a vague symptom name.