Source : Webster's Revised Unabridged Dictionary (1913)

Begum \Be"gum\, n. [Per., fr. Turk., perh. properly queen
   mother, fr. Turk. beg (see {Beg}, n.) + Ar. umm mother.]
   In the East Indies, a princess or lady of high rank.
   --Malcom.

Source : WordNet®

begum
     n : a Muslim woman of high rank in India or Pakistan