D defs.my
Entry 1 sense Webster, 1913

Preignition

/prēˌ-əg-nĭsh'-ən/ · Pre·ig·ni·tion · IPA /prˌiːəɡnˈɪʃən/
01 n. Ignition in an internal-combustion engine while the inlet valve is open or before compression is completed.
  1. 1.
    Ignition in an internal-combustion engine while the inlet valve is open or before compression is completed.(Engin.)