Picture of the former Australian cricketer Len Darling taken in the 1930s. The image is pre-1955 and therefore is in the public domain. ...
• (n.) Ignition in an internal-combustion engine while the inlet valve is open or before compression is completed.
Pre`ig·ni'tion noun (Engineering) Ignition in an internal-combustion engine while the inlet valve is open or before compression is completed. 
preignition, pre-ignition 1. The ignition of the fuel mixture in a gasoline engine cylinder before normal ignition by the spark plug, typically caused by overheated plug points. This results in an inefficient, rough-running engine. 2. Ignition of fuel in an internal-combustion engine before the spark has been generated, causing inefficient operat...
ignition of the charge in an internal-combustion engine earlier in the cycle than is compatible with proper operation.