“Allahu akbar” means Allah is greater, i.e., greater than your god. It’s a declaration of superiority. Jihad mass murderers the world over scream “Allahu akbar” as they murder people. 9/11 hijacker Mohamed Atta reminded himself to “shout, ‘Allahu Akbar,’ because this strikes fear in the hearts of the non-believers.”
(Thanks to Medforth.)