Definition of knock
of knocking (as on a door
or in an engine
or bearing); "the knocking grew louder"
rap with the knuckles; "knock on the door"
against with force
or violence; "My car bumped into the tree"
a car engine
that is firing
too early; "the car pinged when I put in low-octane gasoline"; "The car pinked when the ignition
was too far retarded"