I ofter read the term "Psychotronic". What exactly does this mean and where does this term come from? It seems to be related to the Sci-Fi and Horror genres.
It is just a different version of the word "parapsychology"
From the Dictionary:
of or relating to a genre of usually low-budget movies that includes horror, fantasy, science-fiction, and underground films.
From psyche + electronics, coined during the Iron Curtain decades after French term psychotronique attributed to engineer Fernand Clerc, who proposed it in November 1954's number of journal ‘Vie des Métiers’ (translatable as "Life of profession"), defining it as "use of thought and will" [...]
In the late 1960s the term was popular among parapsychology researchers of the socialist bloc (particularly Zdeněk Rejdák, a prolific Czech scientist), and admittedly used to dub the term parapsychology to avoid its negative connotations, "to advance parapsychology as a science" (as stated in the Constitution of the Parapsychological Association in 1957) and because apparently, other than the desired scientific aptitude and status it lacked the concept of energy, which is found now in the desinence electronics. The term was then popularized in the western world during the second half of the Cold War by science fiction and fears of mind control.
The Parapsychology itself is:
Parapsychology is the study of alleged psychic phenomena (extrasensory perception, as in telepathy, precognition, clairvoyance, psychokinesis, a.k.a. telekinesis, and psychometry) and other paranormal claims, for example related to near-death experiences, synchronicity, apparitional experiences, etc. It is considered to be pseudoscience by a vast majority of mainstream scientists, in part because, in addition to a lack of replicable empirical evidence, parapsychological claims simply cannot be true "unless the rest of science isn't."
So the movie can be called "psychotronic" if its plot revolves around telepathy, clairvoyance, mind control etc.