Wiktionary
ass crack
alt. (context anatomy vulgar slang English) The gluteal cleft. n. (context anatomy vulgar slang English) The gluteal cleft.
Usage examples of "ass crack".
Did I ever tell you about the time the Prince of England came here, and I was supposed to be security, and I was wearing this tux, but my Jockey shorts kept riding up in my ass crack and were strangling my balls.
For a moment it seemed as though Lori were going to make some smart-ass crack at the old man, but she caught Ryan's eye and kept silent.