Full Idea
For something to be a primary being ('proté ousia') is for it to be a being, something that is, simply in virtue of itself ('kath' hauto') and not in virtue of its relation to other things.
Gist of Idea
Primary being ('proté ousia') exists in virtue of itself, not in relation to other things
Source
report of Aristotle (Metaphysics [c.324 BCE], ousia) by Vassilis Politis - Aristotle and the Metaphysics 1.3
Book Reference
Politis,Vasilis: 'Aristotle and the Metaphysics' [Routledge 2004], p.11
A Reaction
From that it sounds as if everything which exists has primary being. Can something have being in relation to other things if it has no existence in itself?