Well in France, most people just say "un stop", you don't need to precise it is a sign, because it was originally a borrowed word
préciser = to precise
I like that. :-) Or maybe 'precisify'.
On the other hand "precisar" in Portuguese is "to need", Spanish like French is "to specify" ... keeping a slew of these cognates straight between English/Spanish/Portuguese is a harder part of dealing with all three.
"préciser" in English is "specify" in case that helps. (This has been a lovely thread!)
Oups
I usually hear people say "un stop" or "un arrêt", not both.