The word disimprove means to deteriorate or worsen. There are various synonyms of the word disimprove that can be used alternatively depending on the context. Some of the most common synonyms of the word disimprove include decline, regress, deteriorate, degenerate, worsen and decay. All these words are used when something is getting worse or deteriorating over time.
For instance, instead of saying that the quality of the product has disimproved, one can say that the quality has declined, or worsened. Similarly, if someone's health is getting worse, we can replace the term disimprove with the word deteriorate or regress. Further, we can use these words interchangeably to convey similar meanings in different contexts.