"Don't even think about/of doing something" is a popular idiom that means a person should definitely not do something. Some of the synonyms for this phrase include "forget about it," "don't even try," "not a chance," "out of the question," "absolutely not," and "never in a million years." These phrases are commonly used to emphasize that a certain action is not up for consideration. When someone says these phrases, they are indicating that the proposed action is inappropriate or impossible for a variety of reasons. Overall, these alternatives for the phrase effectively convey a strong sense of denial or rejection towards a specific course of action.