The term that describes the rapid movement of particles back and forth is vibration.

Here's why:

* Vibration refers to a periodic motion of a particle or object about a central point or equilibrium position. This back-and-forth movement can occur at various frequencies and amplitudes.

* Oscillation is a similar term, but it often implies a more regular and predictable movement.

So, while both terms can be used to describe the back-and-forth movement of particles, vibration is the more general term.