According to Google, Bismillah means:
in the name of God (an invocation used by Muslims at the beginning of an undertaking).
But, is that the same context in which it is used? If not, then what does it mean in context of the song?
There was apparently an official explanation given for the use of the word:
In 2004, Queen's Greatest Hits became the first rock album allowed in Iran. The cassette came with an explanatory leaflet which insisted the hero "killed a man" by accident, then sold his soul to the devil. On the night before his execution he calls God in Arabic - "Bismillah" - and so regains his soul from Satan.
Of course given the market in which the product was released, this could be seen as a non-definitive interpretation of the reason for the use of the word. However, it does at least confirm that the word is indeed Bismillah and used in its normal meaning.
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