The Collaborative International Dictionary of English v.0.48:

mu'adhdhin \mu'adhdhin\ n.
   Same as muezzin.
   [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

muezzin \mu*ez"zin\ (m[-u]*[e^]z"z[i^]n), n. [Ar.]
   A Mohammedan crier of the hour of prayer; the Moslem official
   of a mosque who summons the faithful to prayer from a minaret
   five times a day. [Written also mouezzin, mueddin,
   muazzin, mu'adhdhin, and muwazzin.]
   [1913 Webster + WordNet 1.5]