psi

noun

1. (countable)The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.
2. (uncountable)A 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.’”

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

   “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.”

3. (abbreviation, alt-of, initialism)Initialism of pre-sentence investigation.
4. (abbreviation, alt-of, initialism)Initialism of protein structure initiative.
5. (abbreviation, alt-of, initialism)Initialism of pollutant safety/standard index (measurement of the air pollutant such as haze).

symbol

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).”

name

1. (UK, abbreviation, alt-of, initialism)Initialism of Policy Studies Institute, a British think tank.