Gilt-edge is an adjective used to describe something that is of the highest quality or extremely valuable. However, there are several antonyms for gilt-edge. One of them is "inferior," which means something that is lower in quality or below average. Another antonym is "commonplace," which refers to something that is ordinary or predictable. "Mediocre" is also an antonym for gilt-edge, meaning that something is average or not particularly good. "Unimpressive" is another antonym for gilt-edge, indicating that something does not meet high standards or expectations. Other words that can be used as antonyms for gilt-edge include "substandard," "mediocre," and "ordinary.