psi

1 of 3

noun (1)

ˈsī How to pronounce psi (audio) ˈpsī How to pronounce psi (audio)
: the 23rd letter of the Greek alphabet see Alphabet Table

psi

2 of 3

noun (2)

ˈsī How to pronounce psi (audio)
: parapsychological psychic phenomena or powers

psi

3 of 3

abbreviation

pounds per square inch

Word History

Etymology

Noun (1)

Middle English, from Medieval Latin, from Late Greek, from Greek psei

Noun (2)

probably by shortening & alteration from psychic

First Known Use

Noun (1)

15th century, in the meaning defined above

Noun (2)

1942, in the meaning defined above

Time Traveler
The first known use of psi was in the 15th century

Phrases Containing psi

Rhymes for psi

See All Rhymes for psi

Browse Nearby Words

pshaw
psi
PSIA
See all Nearby Words

Cite this Entry

“Psi.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/psi. Accessed 23 Apr. 2025.

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Kids Definition

psi

noun
ˈsī
: the 23rd letter of the Greek alphabet
—Ψ or ψ

Medical Definition

psi

1 of 2 adjective
ˈsī How to pronounce psi (audio)
: relating to, concerned with, or being parapsychological psychic events or powers
psi phenomena

psi

2 of 2 noun
: psi events or phenomena
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