: the 23rd letter of the Greek alphabet see Alphabet Table


2 of 3

noun (2)

: parapsychological psychic phenomena or powers


3 of 3


pounds per square inch

Examples of psi in a Sentence

Recent Examples on the Web
Grizzlies are right behind them with a bite force of 1,160 psi. Matthew Every, Field & Stream, 6 Sep. 2023 Atmospheric pressure at sea level is 14.7 psi, according to NOAA, the National Oceanic and Atmospheric Administration. Shannon Sollitt, The Salt Lake Tribune, 5 Sep. 2023 The tubes are then filled with water at a pressure of 5000 psi, which forces them into their four-by-six-inch rectangular configuration. Csaba Csere, Car and Driver, 7 Sep. 2023 The paint is a standard exterior grade latex paint in a 5 gallon bucket on the ground where a 3,300 psi airless paint compressor pumps the material via a tether (the blue hose) to the drone. Evan Ackerman, IEEE Spectrum, 20 Apr. 2018 The inflator can handle a maximum inflation pressure of 150 psi, with high-pressure and high-volume inflation modes for tackling different jobs, including filling up vehicle tires and air mattresses. Brandon Russell, Popular Mechanics, 28 June 2023 And one computer modeling study has estimated that a relatively large great white shark could sink its teeth into prey with a force of almost 4,000 psi. Sophie Bushwick, Scientific American, 21 June 2023 Several of us wondered if somehow the tires had been inflated to, say, 60 psi. Steven Cole Smith, Car and Driver, 6 July 2023 That’s why the pressure at sea level is often characterized as one atmosphere, a unit equivalent to almost 15 pounds per square inch (psi). Sophie Bushwick, Scientific American, 21 June 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'psi.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


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

Dictionary Entries Near psi

Cite this Entry

“Psi.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/psi. Accessed 19 Apr. 2024.

Kids Definition


: the 23rd letter of the Greek alphabet
Ψ or ψ

Medical Definition


1 of 2 adjective
: relating to, concerned with, or being parapsychological psychic events or powers
psi phenomena


2 of 2 noun
: psi events or phenomena
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