Other forms: crusading; crusades; crusaded
If you go on a crusade against vegetables, you are waging a long-term battle against leafy greens. A crusade is a passionate struggle against something or someone.
In the 11th through 13th centuries, Roman Catholics attempting to win control of parts of what they considered the Holy Land (currently Israeli, Jordanian, Lebanese, and Palestinian lands) waged military battles against the Muslims who controlled the land. These battles are called the Crusades. The word crusade carries with it the feeling of a violent and vigorous fight. So if someone is on a crusade to do something, they mean business!