What is the meaning of Crusade?

noun

• A series of actions advancing a principle or tending toward a particular end.
  • usage: "he supported populist campaigns"; "they worked in the cause of world peace"; "the team was ready for a drive toward the pennant"; "the movement to end slavery"; "contributed to the war effort"
  • synonyms: campaign, cause, drive, movement, effort
• Any of the more or less continuous military expeditions in the 11th to 13th centuries when Christian powers of Europe tried to recapture the Holy Land from the Muslims.

verb

• Exert oneself continuously, vigorously, or obtrusively to gain an end or engage in a crusade for a certain cause or person; be an advocate for.
  • usage: "The liberal party pushed for reforms"; "She is crusading for women's rights"; "The Dean is pushing for his favorite candidate"
  • synonyms: fight, press, campaign, push, agitate
• Go on a crusade; fight a holy war. .