ignition of the charge in an internal-combustion engine earlier in the cycle than is compatible with proper operation.
Origin of preignition
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
ignition of all or part of the explosive charge in an internal-combustion engine before the exact instant necessary for correct operation
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012