PIVOT

A thing on which something turns; specifically a metal pointed pin or short shaft in machinery, such as the end of an axle or spindle.

(by extension) Something or someone having a paramount significance in a certain situation.

Act of turning on one foot.

The officer or soldier who simply turns in his place while the company or line moves around him in wheeling.

To turn on an exact spot.

To make a sudden or swift change in strategy, policy, etc.