The three letters represent the three worlds - the gross earth, the subtle atmosphere and the causal heaven - as well as the powers of - creation, preservation and destruction or
Generation - Organization - Dissolution = GOD
Another description is the following:
"GOD is an isotropic line parallel to itself and vibrating on itself at right angles. He is like a system of Axis's in which the point of intersection of the lines is everywhere at the same time."  The meaning of the word "Isotropic": That which exhibits equal physical actions in all directions. Light is a case in point. Furthermore...
'Man can only truly understand the phenomena of nature when he understands the nature of God'  
- Dino Kraspedon,  'My Contact With UFOs'

Brahman (God) is the Self (Atma), hidden in everyone. He is only obvious to those whose minds are focused one- pointedly on the Lord of Love, nurturing intuitive knowledge. Meditation leads them deeper into consciousness, passing from the world to thoughts, and beyond thoughts to the wisdom of the Self.  - Katha Upanishad.
"I am in all things, from Brahma to a blade of grass." When you know this, you have no thought for success or failure or the mind's inconstancy. You are pure. You are still.   -  Ashtavakra Gita 11:7
He who knows Self as the enjoyer of The honey from the flowers of the senses, ever present within, ruler of time, goes beyond fear. For this Self is Supreme!   - Upanishads (c. B.C. 800)
When the solution is simple, God is answering  -   Albert Einstein
In happiness and suffering, in joy and grief, we should regard all creatures as we regard our own self. - Jainism

Worship of God in temples and shrines has its place in sanctifying time and sublimating the instincts and impulses. Inquiry into reality has its use in clearing the fog of doubt. But activity in the shape of service charged with love fulfills the aims of our path to God. All hands are HIS, all feet, all eyes and all faces and mouths are HIS. He works through all hands, HE works through all feet; HE sees through each eye; HE eats and speaks through each mouth.  Every- thing is HE. Every step is HIS, every look, every speech, every act is HIS. That is the lesson that service instills. - SSSB

GOD is, therefore, a metaphysical word that refers to and describes the intelligent creative energy animating the process of creation from beginning to end, from generation to dissolution.

Do not cage God in a picture,

Do not confine Him in an Idol,

He is all forms, He is all Names. 

Sri Sathya Sai Baba