I guess terrible is unfair. But the difference between alef and heh is an important phonemic distinction and it makes it almost impossible for me to follow speech, and I've been doing Hebrew off and on (though admittedly I have no ear for languages and think they're much easier to learn to read, and even to speak, than to understand by listening.)
In English, you can't tell without a specific person/noun that you are telling. Basically, you say something, but tell someone.
Well, I'd say it's not that clear cut. Yes, as a secondary translation, I'd say it's possible. But for its primary translation, you'd need the verb להתכוון and your sentence would be: מה הוא מתכוון? What does he mean?
On the other hand מה זאת אומרת? means "What does it mean?" but that is a set phrase and from my understanding a formal one, which can have a secondary translation "what do you mean?". And also there is the colloquial מה זה אומר? with the same meaning.