What is the meaning of God?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Ar-Rab (God) is He Who is worshipped and to Whom His Servants dedicate their intention and acts of obedience. The One Who deserves this   worship is Allaah, as all mankind acknowledge that it is He Who Created the heavens and the earth, and it is He Who Created them and Provides for them. Allaah Says (what means): {And if you should ask them, “Who has created the heavens and the earth?” they would surely say, “They were created by the Exalted in Might, the Knowing,”} [Quran 43:9]

Allaah also Says (what means): {And if you asked them who created them, they would surely say, “Allaah.” So how are they deluded?} [Quran 43:87]. Allaah further Says (what means): {Allaah is the one who created you, then provided for you, then will cause you to die, and then will give you life. Are there any of your “partners” who does anything of that? Exalted is He and high above what they associate with Him.} [Quran 30:40].

Therefore, it is Allaah only Who has the right to be worshipped and whoever is worshipped beside Him, is nothing but a false God. This is the meaning of the word of monotheism Laa Ilaaha Illa Allaah (None has the right to be worshipped except Allaah).  

Allaah Knows best.