There are several synonyms for the term "warning sign." Some of the most common include "cautionary signal," "red flag," and "alert." Other options might include "precautionary measure," "notice," or "advisory." When selecting a synonym for "warning sign," it's important to consider the specific context of the situation. For example, in some cases a "prophylactic" measure might be more appropriate, while in others a "heads-up" might suffice. Ultimately, it's important to choose a synonym that accurately conveys the nature and severity of the potential danger in question. By doing so, we can help people stay safe and avoid unnecessary risks.