psi

plural psis

1. countableThe twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.
2. uncountableliteratureA form of psychic energy.

   ‘Come, lad,’ he said. ‘We will take tea together and speak of the noumenon, the psi and other more heterogenous phenomena.’

   1993, Will Self, My Idea of Fun

   2 more examples

   When an event is classified as a psi phenomenon, it is claimed that all known channels for the apparent interaction have been eliminated.

   1996, Michael F. Stoeber, Hugo Anthony Meynell, Critical Reflections on the Paranormal (page 60)

   It traces the growth of homo gestalt with the uniting of six lovely outcasts of society who have psi powers and come together as a hive mind, thus creating a gestalt super-being.

   2005, Michael Ashley, Transformations: The History of the Science Fiction Magazine 1950 to 1970, Liverpool: Liverpool University Press, page 133

alternative P.S.I. · alternative PSI

1. Pound per square inch (an imperial unit of pressure)

   For M2, this is typically around 3250 MPa (471,000 psi) when tempered at 300°F (149°C).

   2024 March 23, “Yield Strength of Steel: A Comprehensive Guide”, in Unionfab, archived from the original on 13 Jan 2026

   1 more example

   Each turbogenerator consisted of a steam turbine, powered by 900 psi of superheated steam, that was coupled by a set of reduction gears to a General Electric marine alternating-current generator operating at 1,800 rpm. Each generator had a capacity of 2,000 kilowatts of three-phase power at 450 volts and 60 hertz. The main 450-volt switchboard was energized by the two turbogenerators. The emergency switchboard, in the emergency generator room, was fed from the main switchboard through an electrical tie.

   2017 December 12, National Transportation Safety Board, “1.3.5 Electrical Generation and Distribution System”, in Marine Accident Report: Sinking of US Cargo Vessel SS El Faro, Atlantic Ocean, Northeast of Acklins and Crooked Island, Bahamas, October 1, 2015, archived from the original on 15 May 2022, pages 36–37

1. abbreviationinitialismInitialism of pre-sentence investigation.
2. abbreviationinitialismInitialism of protein structure initiative.
3. abbreviationinitialismInitialism of pollutant safety/standard index (measurement of the air pollutant such as haze).

1. UKabbreviationinitialismgovernmentInitialism of Policy Studies Institute, a British think tank.