psiPronunciation: /psʌɪ, sʌɪ/Definition of psi noun 1the twenty-third letter of the Greek alphabet (Ψ, ψ), transliterated as ‘ps’. (Psi) [followed by Latin genitive] Astronomy the twenty-third star in a constellation:Psi Aquarii 2 [mass noun] supposed parapsychological or psychic faculties or phenomena: [as modifier]:psi powersOrigin:Greekpsi in other Oxford dictionaries Definition of psi in the US English dictionary
