By what I know, holy mean dedicated to God. Could God be dedicated to God? I think not, because God is God. This is why it is maybe better to say just that God is spirit.
Bible tells about Holy Spirit:
But the Counselor, the Holy Spirit, whom the Father will send in my name, he will teach you all things, and will remind you of all that I said to you.
John 14:26
When the Counselor [Greek Parakletos: Counselor, Helper, Advocate, Intercessor, and Comfortor.] has come, whom I will send to you from the Father, the Spirit of truth, who proceeds from the Father, he will testify about me.
John 15:26
However when he, the Spirit of truth, has come, he will guide you into all truth, for he will not speak from himself; but whatever he hears, he will speak. He will declare to you things that are coming.
John 16:13
I believe that means, Holy Spirit is like state of mind that leads person towards truth.