How to Conceive of the Greatest Being

I understand that the words make sense to me, but it's wrong to assume that therefore, I have actually conceived it. How do we know that the greatest conceivable being actually is something that we can conceive of? Because we can understand the words. If you say a square circle, I know what you mean in terms of what you're getting at. You're getting at a contradiction. But if I try to actually understand what is a squarecircle, what is something that has four sides and also one side, to me, that's just senseless. That's almost what makes it a contradiction is the fact that no, you can't understand what that is. And you can understand it being