Top notch is a phrase used to describe the highest level of quality. However, there are many antonyms for this phrase that describe something of a lesser quality. For instance, some antonyms for top notch include low-quality, inferior, substandard, mediocre, or second-rate. These words can be used to describe products, services, or experiences that are not up to par with the best in their field. When comparing something that is top notch to something that is low-quality, the differences are stark. So, while top notch is an incredibly positive term, its antonyms are demotivating and highlight a product's flaws rather than its strengths.