It is the plural imperative form of the verb "arrêter", which means "to stop" or "to arrest".
Here are some examples of how "arretez" can be used:
* Arretez! - Stop!
* Arretez de parler! - Stop talking!
* Arretez-vous ici. - Stop here.
* Arretez le camion! - Stop the truck!
It's important to note that "arretez" is a formal command, and in informal situations, you might use "arrête" (singular) or "arrêtez" (plural) instead.