- any of the military expeditions undertaken by the Christians of Europe in the 11th, 12th, and 13th centuries for the recovery of the Holy Land from the Muslims.
- any war carried on under papal sanction.
- any vigorous, aggressive movement for the defense or advancement of an idea, cause, etc.: a crusade against child abuse.
- to go on or engage in a crusade.
- any of the military expeditions undertaken in the 11th, 12th, and 13th centuries by the Christian powers of Europe to recapture the Holy Land from the Muslims
- (formerly) any holy war undertaken on behalf of a religious cause
- a vigorous and dedicated action or movement in favour of a cause
- to campaign vigorously for something
- to go on a crusade
