1. The 23rd letter of the Greek alphabet
   "Psi is often used as a symbol in psychology and parapsychology"
    
2. A unit of pressure
   "The tire pressure was specified as 32 psi";
   - pounds per square inch

Sounds like: sidle, seidelgh

Derived forms: psis

Type of: alphabetic character, letter, letter of the alphabet, pressure unit

Part of: Greek alphabet

Encyclopedia: Psi, Greece