To Westerners [the word jihad] conjures scenes of screaming fanatics being egged into war by promises that they will be instantly transported to heaven if they are slain. In actuality:
a) jihad literally means exertion, though because war requires exertion in exceptional degree the word is often, by extension, attached thereto.
b) The definition of a holy war in Islam is virtually identical with that of a just war in Christianity, where too it is sometimes called a holy war.
c) Christianity, too, considers those who die in such wars to be martyrs, and promises them salvation.
d) A hadith (canonical saying) of Muhammad ranks the battle against evil within one's own heart above battles against external enemies. "We have returned from the lesser jihad," the Prophet observed, following an encounter with the Meccans, "to face the greater jihad," the battle with the enemy within oneself.
From "The World's Religions" - Huston Smith, 1958 (rev. 1991).