Dictionary.com
Thesaurus.com

Ma'mun, al-

American  
[al-mah-moon, -ma-] / ˈæl mɑˈmun, -mæ- /
Also al-Mamoun.

noun

  1. abu-al-'Abbās 'Abdullāh, a.d. 786–833, caliph of Baghdad 813–833 (son of Harun al-Rashid).