Jihad is an Arabic word that English borrowed. In Arabic it means a struggle or a hard effort — the kind you put your whole self into. In Islam that can mean trying hard to live a good life (some Muslims call this the greater jihad), and it can also mean fighting in a war that is understood as a religious duty (sometimes called the lesser jihad). In everyday English, though, especially in the news, people almost always use jihad to mean a holy war — armed fighting in the name of Islam. That English use is narrower, louder, and more political than the full Arabic idea. Muslims themselves do not all agree on what counts as jihad; people who study this have argued about it for a very long time. As a verb, to jihad is rare and sounds odd to many speakers; the noun is the form you will actually meet. Handle it with care: it is a real religious word, not a joke. Some English speakers stretch it to mean any fierce campaign (“a jihad against junk food”), which many Muslims find careless.