The phrase "top notch" is an idiomatic expression that means something is exceptional, outstanding or of very high quality. It implies that a person or thing has reached the highest level of proficiency in their respective field and is considered to be among the best. The term originated from the practice of placing a knot at the top of a rope to indicate its superior quality, as it was less likely to come undone when tied securely. Today, "top notch" is used in various contexts to describe something that exceeds expectations and is highly praised for its excellence.