It's impossible to translate literally. Μωρέ is the vocative form of μωρό, which means "baby," so your sentence Μωρέ εσύ έισαι μωρό ακόμα! means, literally, "Baby, you're still a baby!" But μωρέ is a much more general term of intimacy than that, and is often (like the related ρε, μπρε, and βρε) meant affectionately. English equivalents would include "man," "buddy," "kid," and "kiddo." And, as with the foregoing English expressions, you can use μωρέ to address either a male or a female.
Μωρέ, however, is far from being a "polite" term of address, and could be considered abusive if used toward a total stranger with whom hostile engagement is not out of the question. In that sense, it would be like "idiot," "jerk," or worse. It is, basically, a demeaning epithet.