Mahdi
Concise Oxford English Dictionary © 2008 Oxford University Press:
Mahdi /ˈmɑːdi/
▶noun (pl. Mahdis)
- 1 (in popular Muslim belief) a spiritual and temporal leader who will rule before the end of the world and restore religion and justice.
■ a person claiming to be this leader, notably Muhammad Ahmad of Dongola in Sudan (1843–85).
- 2 (in Shiite belief) the twelfth imam, who is expected to return and triumph over injustice.
– derivatives
Mahdism noun,
Mahdist noun & adjective.
Mahdism noun,
Mahdist noun & adjective.
– origin from Arab. (al-)mahdī ‘he who is guided in the right way’.
'Mahdi' also found in these Oxford entries:

