psi

¹ American  

Or p.s.i.

1. pounds per square inch.

---

psi ² American  

[sahy, psahy] / saɪ, psaɪ /

noun

plural

psis

1. the 23rd letter of the Greek alphabet (Ψ, ψ).

2. the group of consonant sounds represented by this letter.

---

psi ³ American  

[sahy] / saɪ /

noun

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

---

psi ¹ British  

/ 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 British  

abbreviation

1. pounds per square inch

---

Etymology

Origin of psi²

1350–1400; Middle English < Greek pseî

Origin of psi³

1940–45; shortening of psychic or parapsychic