Source : Webster's Revised Unabridged Dictionary (1913)

Mahout \Ma*hout"\, n. [Hind. mah[=a]wat, Skr. mah[=a]m[=a]tra;
   mahat great + m[=a]tr[=a] measure.]
   The keeper and driver of an elephant. [East Indies]

Source : WordNet®

mahout
     n : the driver and keeper of an elephant