Disclaimer: I do not own Sherlock.
How to: Teach Your Detective Euphemisms
Sherlock reclined on the sofa, stretching happily, still enjoying the afterglow of a solved case and at least three days away from putting more bullet holes into Mrs. Hudson's walls. It was John's favorite time, because Sherlock was pleasant (relatively) and talkative and happy.
"So, John," Sherlock asked conversationally, "what did U.M.Q.R.A. end up being?"
He glanced up from the rather boring novel he was reading. "Oh, just some people doing it in a car."
John gave him a funny look. Surely not. "Doing it, Sherlock."
He sat up in that floppy way he did. "Doing what?"
John's mind was blown. Maybe this was to be expected, he pondered. After all, Sherlock wasn't exactly educated in this area. But then, Anderson and Donovan were prime examples that Sherlock was more than capable of deducing when people had been "doing it."
"Having sex?" he offered hesitantly.
"Oh," Sherlock said, instantly uninterested. Why didn't you say so? Really, 'doing it' could mean so many things..."
John shook his head. "No. 'Doing it' always means 'having sex' if there's no qualifier."
"Always. All the time."
"At least as long as I've been alive."
Sherlock huffed. "Well that's terribly confusing. Although..." his lips flattened in acknowledgment, "that would explain that one incident with a goat in Cardiff."
"What... one incident with a goat in Cardiff?"
Sherlock nodded to himself, then flopped back down onto the sofa, content, and John decided he really would rather not know.