What is another term for rapidity of movement?

There are many terms for rapidity of movement, depending on the context and nuance you want to convey. Here are some options:

General terms:

* Speed

* Velocity

* Swiftness

* Celerity

* Haste

* Quickness

* Agility (if it refers to ease and grace in movement)

* Nimble (if it refers to quick and skillful movement)

More specific terms:

* Acceleration (refers to the rate of change in speed)

* Momentum (refers to the mass in motion)

* Impetuosity (implies a lack of control or thought)

* Dash (a sudden and quick movement)

* Whirlwind (implies great speed and force)

* Lightning fast (implies extreme speed)

The best term to use will depend on the specific situation.