Wiktionary
dirty business
n. 1 the practice of unethical methods 2 (context slang English) anal sex
Wikipedia
Dirty Business
Dirty Business may refer to:
Usage examples of "dirty business".
If her husband were mixed up in some dirty business, she would just have to hope that Cy would never hear about it.
She had done the dirty business on the other, it was plain: but she seemed deserted, too.
He fidgeted nervily around, occasionally grabbing the handhold heartily wishing the whole dirty business were done with and over.
I've heard about this dirty business of military eptification and it strikes me as the foulest thing one man can do to another, worse by far than killing him clean!