Webster's Revised Unabridged Dictionary · 1913

Islam

Islam , proper noun

[Arabic islām obedience to the will of God, submission, humbling one's self, resigning one's self to the divine disposal. Compare Moslem.]

1.
The religion of the Muslims; Islamism. Their formula of faith is: There is no God but Allah, and Mohammed is his prophet. An older term is Mohammedanism, but this term is considered offensive by many Muslims, as their submission is to Allah, not Mohammed.
2.
The whole body of Muslims, or the countries which they occupy.