Stop always means stop - it's not a word for discussion or a word used to initiate an interview. It simply means what it says - stop.
The inability among certain men to understand that specific four-letter word is why rape is such a common criminal act. But then four letters sometimes surpass the intellectual capacity of men...
again it isn't on you to determine what someone elses fantasy is nor is it up to you to decide which safeword they are and are not permitted to use
you just are not as special as you seem to think you are
the inability of certain females (namely you) to understand that she might be acting out a fantasy is why mislabeling sex as rape is so common on the internet but then ignorance is often the favored crutch of women ;O)