I also think 'spoilt' means different things to different people - for instance, there were several replies in this thread from people who didn't think they were spoilt, which I read and thought; "Gosh, that's almost the definition of spoilt!!". Just because I think they're spoilt doesn't mean they or anyone else would think that.
Am I spoilt as an adult? Yes and no. I have nice things, and a comfortable lifestyle, yes. However, I have zero debt, and I can honestly say, hand-on-heart, that every single thing I have, I worked for. So in that respect, no, I am not spoilt.
I think being spoilt as an adult means one of two things: either being given extravagant gifts or large sums of money, or getting into debt to buy pointless stuff that you could really live without.
I hope when I have kids I can give them more than I had as a child, but I certainly won't be showering them in material possessions.