Abridged means that some of the original text of a book has been altered or removed.
In the case of the Harry Potter books [J.K.Rowling] it is likely that the American version[s] of the books have been abridged to suit a US readership.
While UK and USA do indeed share a common language, there are major differences in usage, even while the words themselves remain 'English'.
For example. When you want to check the engine in your car, you lift the 'hood'. Here in UK we lift the 'bonnet'. Two perfectly ordinary English words which describe head gear or hats.
It gets worse, but don't worry, the UK version of Harry Potter is not going to be in a 'foreign language', it will be English as she is spoke in UK and Ireland.
Try this UK link and see if you can buy a copy on line.
WHSmith.co.uk: On-line retailer with over 1 million Books, 100000 DVDs and CDs and over 450 Magazines
http://www.whsmith.co.uk/whs/go.asp
W.H.Smith is a major high-street and shopping mall book store. Got a shop in every town here in UK.
If you want swear words, as suggested by someone on here, try reading The Canterbury Tales by Geoffrey Chaucer - just about every other words is a four letter expletive.