Dictionary

Any of the military expeditions undertaken by the Christians of Europe in the 11th to 13th centuries to reconquer the Levant from the Muslims.

Example: During the crusades, many Muslims and Christians and Jews were slaughtered.

Any war instigated and blessed by the Church for alleged religious ends. Especially, papal sanctioned military campaigns against infidels or heretics.

A grand concerted effort toward some purportedly worthy cause.

Example: a crusade against drug abuse

A mass gathering in a political campaign or during a religious revival effort.

To go on a military crusade.

To make a grand concerted effort toward some purportedly worthy cause.

Example: He crusaded against similar injustices for the rest of his life.