PRI: Personal Record Identifier (Canada) PRI: Periodic Reinvestigation: PRI: Preliminary Rifle Instruction: PRI: Planning, Review, and Inspection: PRI: Progressive Routing Indicator (US DoD) PRI: Prisoner Reentry Initiative (various locations) PRI: Policy Research Institute (various locations)
Adding definition, to unite or join so as to increase the number, quantity, size, or importance: to add two cups of sugar; to add a postscript to her letter; to add insult to injury. See more. Dictionary.com
Noun. 1. addition reaction-a chemical reaction in which one molecule is added to another. chemical reaction, reaction - (chemistry) a process in which one or more substances are changed into others; there was a chemical reaction of the lime with the ground water. 1  Facebook. 2  Twitter.