Of or pertaining to Mohammed, or the religion and institutions founded by Mohammed; in the latter sense, synonymous with Islamic, the term preferred by Moslems.

A follower of Mohammed, the founder of Islam (also called Islamism or Mohammedanism); an adherent of Islam; one who professes Mohammedanism or Islamism; a Muslim; a Moslem; a Musselman; -- this term is used mostly by non-Moslems, and some Moslems find it offensive.

a believer or follower of Islam

of or relating to the Arabian prophet Muhammad or to the religion he founded

Mohammedan (variant form: also Muhammadan) is a term used as both a noun and an adjective meaning belonging or relating to either the religion of Islam or to that of its last prophet Muhammad. The term is now largely superseded by Muslim, Moslem or Islamic but was commonly used in Western literature until at least the mid 1960s. (See for instance the second edition of "A Dictionary of Modern English Usage" by HW Fowler, revised by Ernest Gowers (Oxford, 1965)).