Allahu Akbar:-
This is a cry of Glorification (Takbir) meaning 'Allah is greater'. Contrary to the general perception, this was a cry used by the Pagan Arabs long before Muhammad and his Quran (Ishaq 62).
It meant that the god Allah was GREATER than all the other 360 gods and godesses in the pantheon of the pagan Arabs.
This pagan tradition also, was absorbed , subsumed and 'Islamized' by Muhammad into his new Cult Belief System and constantly used as a TERRORISING battle cry by him and his followers.
In fact this expression is also used when animals - as well as humans - are being slaughtered.
Bukhari Sahih Hadith 5.456
"Muhammad led the Fear/ Terror Prayer [Allahu Akbar] with one batch of his army while the other (batch) faced the enemy."
** This is also called the TERROR VERSE by the Muhammadan exegetes ***
Bukhari Sahih Hadith 5.516
"When Allah's Apostle fought or raided people we raised our voices saying, 'Allahu-Akbar! Allahu-Akbar! None has the right to be worshipped but Allah.'"