Quoted from the Words With Friends rulebook at http://newtoyinc.com/gameswithfriends/support/Words_With_Friends_Rulebook.html :
Words With Friends uses the Enhanced North American Benchmark Lexicon (ENABLE): Originally released in 1997 and updated in 2000. This list of 173,528 words has been in the Public Domain since its release. Tap here to visit the site where the word list resides. We've added a few of our own words to the dictionary such as ‘zen’ and ‘texting,’ and more words may be added in the future.
When I look in the ENABLE wordlist at that link, I see that URIC is included in it. So if you tried to play URIC in Words With Friends and saw a message saying that the word was unplayable, I'm not sure why that would have happened. Since Zynga now owns Words With Friends, it looks as though any requests to add words to the WWF dictionary should be sent to them.