I THINK most students of the languages involved would say that that is a Semitic superlative form. The way I think of it is, "You got your rams; among them THAT one is the big one." Which comes down to, "That's the biggest ram."
That's one of those gems that can lead to a fresh re-reading of the New Testament. It might lead one to remember that hellenics interpreting what is basically a hebraic text need to be very careful not to overextend the interpretation.