It's "poseur".

While I'm on the subject of abuses of the English language, here's another thing that has gotten my goat for a long time, but I've never written about publicly. If you're describing someone who pretends to be something he or she is not, the word is "poseur", not "poser". Compare the two definitions with the links provided (check both definitions of "poser" you'll find there) -- neither of them apply.

Yes, they are pronounced essentially the same way in English, and yes the etymology of the word "poseur" is the same as that of "poser," but there is a reason we have both words in English: so that we can be specific and exact when we speak. If you say one thing when you mean another, it should be from wit, not ignorance.