(Did you mean the Lyle Amlin fanzine?)
Psionics, or psi, is, basically, a scientific dress on magic: Using the power of the mind to accomplish things in the real world without the mediation of the body. It includes telepathy, teleportation, clairvoyance and telekinetics.
It was one of the pseudoscientific hobbyhorses that John W. Campbell started to ride in the 1950s (others included the Dean Drive and — ptui! — Dianetics). They were dressed more scientifically than the Shaver Mystery promoted by Ray Palmer, and probably (unlike the Shaver Mystery), were in large part an honest attempt on Campbell's part to widen the bounds of scientific orthodoxy, but in the end they were garbage.
Campbell's insistence on stories that played to his own unorthodox orthodoxy hastened the fall of Astounding from the pinnacle of SF to just another prozine. Not all the psionics stories were bad, of course, but they tended towards a dreadful sameness.
Entry in The Encyclopedia of Science Fiction
|From Fancyclopedia 2, ca. 1959|
|The things they study in the field of parapsychology; telepathy, ESP, precognition, telekinetics, and allied mental phenomena. Some call it psychophysics.|
|This is a fanspeak page. Please extend it by adding information about when and by whom it was coined, whether it’s still in use, etc.|