Sorry, but there's no specific list of what is allowed/isn't allowed. All they say about language in in the terms of service is:

3.3 Profanity and Offensive Language. You may not use profanity or any language that a reasonable person would find offensive. The Game is for players aged 13 and older. You agree to behave accordingly.
So really you need to interpret that how you think best, but it's probably better to err on the side of caution.