Definitions for kingboltˈkɪŋˌboʊlt
Random House Webster's College Dictionary
a vertical bolt connecting the body of a vehicle with the fore axle, the body of a railroad car with a truck, etc.
Origin of kingbolt:
kingbolt, kingpin, swivel pin(noun)
bolt that provides a steering joint in a motor vehicle
The main bolt of a structure, especially the bolt in a motor vehicle that links the chassis to the axle, providing the steering pivot.
a vertical iron bolt, by which the forward axle and wheels of a vehicle or the trucks of a railroad car are connected with the other parts