Any one of the military expeditions undertaken by Christian powers, in the 11th, 12th, and 13th centuries, for the recovery of the Holy Land from the Mohammedans.
- Any of the military expeditions undertaken by European Christians in the 11th, 12th, and 13th centuries to recover the Holy Land from the Muslims.
- A holy war undertaken with papal sanction.
- A vigorous concerted movement for a cause or against an abuse. See Synonyms at campaign.
- To engage in a crusade.