There are several synonyms for the phrase "go off half-cocked," which refers to behaving impulsively without thinking through the consequences. One alternative is to say someone is "rash," suggesting they act without considering the risks involved. Another similar phrase is "jumping the gun," implying that a person is eager to take action before the appropriate time. Some people might also use the term "reckless," indicating that the individual is acting without regard for safety or the feelings of others. Regardless of the word choice, it is important to take a moment to pause and think through any decision before taking action that cannot be undone.