When a group of workers refuses to work as a form of protest, we commonly say that they "are on strike". However, there are a number of synonyms that can be used to describe this situation. One option is to say that the workers are "boycotting" their work, which typically refers to a more intentional and organized form of protest. Alternatively, you might say that the workers "are on a work stoppage", which emphasizes the cessation of work rather than the protest itself. Another option is to say that the workers "have walked out", which typically suggests a more sudden and spontaneous event. Regardless of which synonym is used, it is clear that the workers are taking a stand and making their voices heard.