psi

¹

[ sahy, psahy ]

noun

, plural psis.

1. the 23rd letter of the Greek alphabet (Ψ, ψ).
2. the group of consonant sounds represented by this letter.

psi

²

[ sahy ]

noun

1. any purportedly psychic phenomenon, as psychokinesis, telepathy, clairvoyance, or the like.

psi

³

or p.s.i.

1. pounds per square inch.

psi

¹

/ psaɪ /

noun

1. the 23rd letter of the Greek alphabet (Ψ, ψ), a composite consonant, transliterated as ps
2. 1. paranormal or psychic phenomena collectively
   2. ( as modifier )

      psi powers

psi

²

abbreviation for

1. pounds per square inch

Word History and Origins

Origin of psi¹

1350–1400; Middle English < Greek pseî

Origin of psi²

1940–45; shortening of psychic or parapsychic

Example Sentences

The military measures the force of blast waves in pounds of pressure per square inch, and the current safety guidelines say that anything below 4 PSI is safe for the brain.

From New York Times

The blast from firing a 120-millimeter mortar officially measures at 2.5 PSI.

From New York Times

My big brother joined Omega Psi Phi Fraternity, Incorporated in the Spring of ’92 and made himself a legend.

From Salon

“He had a strong community of friends from his dorm at Stern Hall and his fraternity Zeta Psi and was thriving academically,” she wrote.

From Los Angeles Times

The experimental proof of a third branch of magnetism, termed altermagnetism, was made at the Swiss Light Source SLS, by an international collaboration led by the Czech Academy of Sciences together with Paul Scherrer Institute PSI.

From Science Daily