Miscellaneous
- Pechersk School International, in Kiev, Ukraine
- Permanent Staff Instructor, in the British Army
- PSI-20, a stock market index of companies that trade on Euronext Lisbon, the main stock exchange of Portugal
- Presentence investigation, in law, an investigation into the history of person convicted of a crime, before sentencing
- Pre-shipment inspection, a method of quality control
- Professional Skills Institute, a private university in Toledo, Ohio
- Pitch Shifter Industries, an acronym used by the British band Pitchshifter
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