\ ˈsī How to pronounce psi (audio) , ˈpsī How to pronounce psi (audio) \

Definition of psi

 (Entry 1 of 3)

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

Definition of psi (Entry 2 of 3)

: parapsychological psychic phenomena or powers

Definition of psi (Entry 3 of 3)

pounds per square inch

First Known Use of psi

Noun (1)

15th century, in the meaning defined above

Noun (2)

1942, in the meaning defined above

History and Etymology for psi

Noun (1)

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

Noun (2)

probably by shortening & alteration from psychic

Keep scrolling for more

Learn More about psi

Time Traveler for psi

Time Traveler

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

See more words from the same century

Statistics for psi

Cite this Entry

“Psi.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/psi. Accessed 29 Feb. 2020.

Keep scrolling for more

More Definitions for psi

\ ˈsī How to pronounce psi (audio) \

Medical Definition of psi

 (Entry 1 of 2)

: relating to, concerned with, or being parapsychological psychic events or powers psi phenomena

psi

noun

Medical Definition of psi (Entry 2 of 2)

: psi events or phenomena

More from Merriam-Webster on psi

Rhyming Dictionary: Words that rhyme with psi

Spanish Central: Translation of psi

Comments on psi

What made you want to look up psi? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

See Definitions and Examples »

Get Word of the Day daily email!

Test Your Vocabulary

February 2020 Words of the Day Quiz

  • squirrel in winter
  • Which is a synonym of probity?
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
Citation

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!