* Noun: A crusade is a religious war, especially one of the medieval expeditions to recover the Holy Land from the Muslims. It can also be used more generally to refer to any vigorous campaign for a cause.
* Verb: To crusade means to campaign vigorously for a cause.
Here are some examples:
Noun:
* "The crusade to end poverty is a long and difficult one."
* "The crusade against drugs has been met with mixed results."
Verb:
* "She crusades for animal rights."
* "They crusaded for better working conditions."