Can someone post a good description of a typcial douche?

I know what a douchebag is but i'm no native english speaker and would like to know what a douche really means. Too many ppl throw that around.

Hitler was no douche that's for sure, he was a maniac that had the balls to take over a whole country politically before he took over half of europe not so politically. Don't know if he qualifies for a douche...