Allahu akbar simply means God is the greatest.
Muslims use this term all time time, for prayers, for praise purposes, innocent purposes not terrorist purposes.
The average redneck\honky pronounciation of the actual sentence "Allah-u Ekber". Which simply means "God is great." 97% of the world being religious and believing in such deity, it is only common American ignorance to believe it is a muslim terrorist chant word. (The idea comes from the beheading videos of victims from the newest Iraqi war President Bush has started.)
Contrary to what *many* have put here, it has nothing to do with terrorism, the devil or deception.
It simply means, "God is great". Allah being Arabic for God. Muslims believe in God and the Holy Qurran does not preach violence on innocents like extremists lead us all to believe.
It is a peaceful saying that extremists use in the wrong context perpetuating the myth of Islam being a violent religion.