When it comes to describing something that is of poor quality, there are plenty of synonyms for the term "third rate." Some possible options include "subpar," "inferior," "mediocre," "second-rate," "low-grade," "shoddy," "below average," and "lousy." Whether you're talking about a product, service, or performance, these terms can help convey the sense that whatever you're describing falls short of expectations. Of course, sometimes you might want to use more colorful language to emphasize just how terrible something is, but even these more mild synonyms can get the point across effectively.