Negative ESP, or "psi-missing," is when you score far below chance in an ESP test. According to the textbook An Introduction to Parapsychology (2007):
It is important to note that this does not indicate a lack of ESP (or of psi in general) since the latter would be associated with nonsignificant scores. Rather, psi missing might be viewed as an expression of psi in a way that produces a result opposite to the conscious intent.
(via Weird Universe)
Article below from the Pittsburgh Post-Gazette (1/19/72):