Source : Webster's Revised Unabridged Dictionary (1913)

Mahatma \Ma*hat"ma\, n. [Skr. mah[=a]tman, lit., great-souled,
   wise.] (Theosophy)
   One of a class of sages, or ``adepts,'' reputed to have
   knowledge and powers of a higher order than those of ordinary
   men. -- {Ma*hat"ma*ism}, n.

Source : WordNet®

mahatma
     n : (Hinduism) term of respect for a Brahmin sage