dictionaries and common usage (e.g. wikipedia, forums, news, etc.) are certainly more authoritative than a random person unilaterally deciding that a word has no meaning and declaring "dictionaries and wikipedia are wrong"

if you poll 100 random english speakers and the majority come back saying that they have no idea what "third world" means, or say that the term is meaningless, i will concede and donate $1,000 to a charity of your choice.

I stated what is very obviously an opinion and never claimed to be an authority