The Meaning of Ar-Rabb, the Lord
Ar-Rabb is the owner who has full authority over his property. Ar-Rabb, linguistically means, the master or the one who has the authority to lead. All of these meanings are correct for Allah. When it is alone, the word Rabb is used only for Allah. As for other than Allah, it can be used to say Rabb Ad-Dar, the master of such and such object. Further, it was reported that Ar-Rabb is Allah’s Greatest Name.
Ar-Rabb is the One Who nurtures and sustains all of His servants through regulating the affairs and granting all types of favours and blessings. More specifically He is the One Who nurtures and sustains his sincere friends by correcting and purifying their hearts, souls and manners. This is why their supplications are frequently made with this Noble Name because they seek this specific nurturing.
Meaning of ar-Rabb, Shaykh Muhammad ibn Saalih al ‘Uthaymeen rahimahullaah states:
Rabb – meaning khaaliq (Creator) and Sovereign Owner and the One who controls; so He is the One who created the heavens and the Earth; and He is the One who owns the heavens and the Earth; and He is the One who controls the heavens and the Earth.
He, the Most High, said:
أَلاَ لَهُ الْخَلْقُ وَالأَمْرُ
Certainly creation and command are His alone. [Soorah al A’raaf (7) aayah 54]
And this is His being unique with regards to His creating and His controlling.
And He, the Most High, said:
وَلِلَّهِ مُلْكُ السَّمَاوَاتِ وَالأَرضِ
And to Allaah belongs the dominion of the heavens and the Earth. [Soorah al Jaathiyah (45) aayah 27]
And this is His being unique in terms of sovereignty.