What is God?

From Radio Replies, By Fr. Rumble and Fr. Carty, Vol. 1 p. 2-3
Q. What do you mean by the term God?
A. God is a spiritual, substantial, personal being, infinite in intelligence, in will, and in all perfection, absolutely simple or lacking composition, immutable, happy in Himself and by Himself, and infinitely superior to all that is or can be conceived apart from Himself. He is incomprehensible in His infinite perfection by all lesser intelligences, although knowable as to the fact of His existence as Living Creator and Lord of Heaven and Earth, almighty, eternal, immense, and distinct from all that He has created. That is what I mean by God.