A "single comic" refers to a standalone comic book or strip that tells a complete story in one issue or panel, independent of any ongoing series or storyline. Full definition
Indigo would not speculate on the reasons why comic sales have tapered off or why Marvel would suspend their relationship with them over single comic sales. (goodereader.com)
Today, they discuss the breaking news of Marvel suspending single comic sales to major bookstores all over the US. (goodereader.com)
The company made their first single comic distribution agreement with Google Books. (goodereader.com)