psi

Etymology

From Ancient Greek ψῖ (psî), the name for the twenty-third letter of the alphabet (Ψ, ψ).

noun

1. (countable) The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.
2. (uncountable, parapsychology, science fiction) A form of psychic energy.
   ‘Come, lad,’ he said. ‘We will take tea together and speak of the noumenon, the psi and other more heterogenous phenomena.’ 1993, Will Self, My Idea of Fun
   When an event is classified as a psi phenomenon, it is claimed that all known channels for the apparent interaction have been eliminated. 1996, Michael F. Stoeber, Hugo Anthony Meynell, Critical Reflections on the Paranormal (page 60)
   It traces the growth of homo gestalt with the uniting of six lovely outcasts of society who have psi powers and come together as a hive mind, thus creating a gestalt super-being. 2005, Michael Ashley, Transformations: The History of the Science Fiction Magazine 1950 to 1970, Liverpool: Liverpool University Press, page 133