The Collaborative International Dictionary
Preignition
Preignition \Pre`ig*ni"tion\, n. (Engin.) Ignition in an internal-combustion engine while the inlet valve is open or before compression is completed.
Wiktionary
preignition
n. (context automotive English) The premature detonation of a fuel charge in http://en.wikipedia.org/wiki/four-stroke%20cycle.
Usage examples of "preignition".
He had heard that one of the preignition pumps had turned up as a vodka still.