Why can't this be translated as "What does THIS word mean"? I thought "to" could mean "this" or "that".
No, "to" means the or that. "This" is toto/tohle.
Why didn't they accept "What does mean that word"?
because is messed up the word order. wait. i have been here before.
Why not "What means the word?"
That's just incorrect in current, everyday English, You might find it in a book or play set in a long-ago time, or possibly in a poem or song.