The "10x rule" is a concept popularized by Grant Cardone in his book titled "The 10X Rule." It suggests that individuals should set goals that are ten times greater than what they initially believe they can achieve. This approach encourages people to think bigger and push beyond their perceived limits, leading to greater success. Additionally, the rule emphasizes the importance of taking massive action to reach these ambitious goals. By committing to a higher level of effort and persistence, individuals can overcome obstacles and achieve results that far exceed their expectations.