cannonball

A spherical projectile fired from a smoothbore cannon.

An explosive-filled hollow iron sphere fused through a hole and intended to explode at a calculated distance rather than explode on impact.

The act of jumping (typically into a swimming pool) with the legs bent and the arms wrapped around the knees to create a large splash, mimicking the flight and shape of a cannonball.

The New Yorker, 30 August 2004, p.40

The cannonball could be called the S.U.V. of the pool — oversized, brash, hormonally hardwired.

Something that moves fast, especially a fast train.

Meetings of the model train club always begin with the song "Wabash Cannonball".

A served ball that travels with great speed and describes little or no arc in flight.

To jump or dive into water, performing a cannonball landing.

He cannonballed into the pool, drenching us all.

To career; to move rapidly.

The car cannonballed past.