First Known Use: 15th century
Dictionary
1psi
noun \ˈsī, ˈpsī\
Definition of PSI
: the 23d letter of the Greek alphabet — see alphabet table
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Origin of PSI
Middle English, from Medieval Latin, from Late Greek, from Greek psei
2psi
noun \ˈsī\
Definition of PSI
: parapsychological psychic phenomena or powers
Origin of PSI
probably by shortening & alteration from psychic
First Known Use: 1942
3psi
abbreviation
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