There are many synonyms for the phrase "not work." Some of the most common ones include "break down," "malfunction," "fail," "stop functioning," "go haywire," "crash," "seize up," and "give out." Other synonyms for this phrase may depend on the context in which it is used. For example, in the context of employment or productivity, synonyms might include "underperform," "fall short," "be unproductive," "be inefficient," or "be ineffective." It's important to be familiar with the range of synonyms for "not work" in order to properly communicate and understand ideas related to efficiency, productivity, and function.