" He cleared his throat. “You need to pick a safe word.”
“What on earth is a safe word?”
He smothered a sigh. This was proving to be more work than he thought it’d be. “It’s a word you use when you want things to stop.”
“How about I use the word ‘stop’?” She sounded sarcastic.
“That’s not how it works. You need a word that you wouldn’t normally use during sex.”
“Fine. How about ‘dumbass’?”
“I don’t think you’re getting into the spirit of this.”
“Really? You think?”
“Fine. Dumbass it is.” There was no dealing with her when she was in this mood. “If you use your safe word, everything stops.”
“Good.” She took a deep breath. “Dumbass,” she shouted.
Andrew wasn’t sure what to do next. This was not going the way it did in the books. "

― Janet Elizabeth Henderson , Goody Two Shoes (Invertary, #2)