I started reading this translation and reached this paragraph:
The nature of the An moved to make the universe. But now either everything that takes place comes by way of consequence or continuity; or even the chief things towards which the ruling power of the universe directs its own movement are governed by no rational principle. If this is remembered it will make thee more tranquil in many things.
...and I'm stumped. I assume it's because I don't understand the context around which this was written or maybe that it's simply poetry or most probably that I'm simply ignorant.
Hmm - for this sort of reason, I've avoided the Long translation. I would suggest looking up the same passage in a more modern translation, and seeing how they translate it (Google Books or a library should be helpful). Ideally, you'd want to find the passage in the original text to isolate the term, but that's a lot of legwork for little more clarity than a modern translation.
I would assume the term is something like the "One". He is talking about a god of some sort, but an important part of MA's outlook is that the precise nature of God is an academic question. Even in this passage, he uses a characteristic tactic of setting out two possibilities for the relation of the divine to the world, and concluding that both are acceptable to the Stoic mindset. He'll even do this for the question of 'God or mere atoms'. As such, while it may be interesting to know the shades of meaning MA attaches to any particular term for God/being/universe/etc., he would likely have considered those subtleties unimportant.