What is the Meaning of "There is no God but Allah?"
It means there is no deity that truly deserves to be worshipped except Allah.
Evidence from the Noble Qur'an
{That is because Allaah, He is the truth and that is which they invoke besides Him is al-Baatil (falsehood, Satan, and all other deities)}, {Soorah al-Hajj, verse 62]
Evidence from the authentic Sunnah
((Whoever says there is no God except Allah and rejects whatever is worshipped besides Allaah, his property and blood become sacrosanct and his reckoning with Allah , the Mighty and Exalted)), [Transmitted by Muslim]