Well, that's the ITU's definition. Unfortunately they didn't acquire the trademark for the 4G designation before carriers already had started to use it on their "slightly better 3G" networks, so there is no regulation on the use of the term in the market.

I think it's funny that AT&T called one of their earlier networks "4G" so now when I have an LTE signal, it doesn't say 4G and when I don't, it does...