What does the word crusade mean?

Usage examples for crusade

  1. The annals of this Ninth Crusade are yet to be written,- the tale of a mission that seemed to our age far more quixotic than the quest of St. Louis seemed to his. – The Souls of Black Folk by W. E. B. Du Bois
  2. He was the preacher of the crusade. – Pius IX. And His Time by The Rev. Æneas MacDonell Dawson