kingpin: Meaning and Definition of

king•pin

1. headpin.
2. the pin at the center; the number five pin.
2. the person of chief importance in a corporation, movement, undertaking, etc.
3. the chief element of any system, plan, or the like.
4. a kingbolt.
5. either of the pins that are a part of the mechanism for turning the front wheels in some automotive steering systems.