"Designer hm? You must be some art guy, what are you doing in the industry then...?" I started explain the real meaning at this point for years, but now I'm tired to do so, I just change the topic of the conversations...
It's the "just" that winds me up as it implies things are really really easy to do. e.g. "why don't you just move everything a bit that way", or "why don't you just change things so this bit fits from the side instead", "why don't you just use a different material..." etc etc. Aaargh!
I agree GarethW. What people are really saying is 'can you 'just' cancel your plans for the weekend!'
True. Especially when asked by your manager, who doesn't have a clue about mechanical engineering, but thinks he has to teach you because he is hierarchically higher than you in the organization.