In the context of comics, DC stands for Detective Comics, which is the name of the comic book publisher that created iconic characters like Batman, Superman, Wonder Woman, and many others. The publisher is officially known as DC Comics.
The “DC” in Detective Comics was originally part of the title of a comic book series launched in 1937. Over time, “DC” became synonymous with the publisher itself. Today, DC Comics is one of the two major comic book companies, alongside Marvel Comics.