In my terms this means the human ability to influence matter with the mind without direct contact. But this is very broad and Stephen E Braude has a better one:
Page 21, ESP and Psychokinesis - A Philosophical Examination (Revised Edition) Universal-Publishers, 2002 - 234 pages
PK is the causal influence of a person (organism) on a physical system (s) without any know sort of (or scientifically recognized) physical interaction between the person's (organism's) body and physical system.
– Stephen E Braude