Meaning

noun a series of actions advancing a principle or tending toward a particular end

noun 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

originFrom French croisade, introduced into English (in the French spelling) by 1575. The modern spelling emerges c. 1760,. Middle French croisade is introduced in the 15th century, based on Spanish cruzada (late 14th century) and Old Occitan crozada (early 13th century), both reflecting Medieval Latin cruciāta, cruxiata, the feminine singular of the adjective cruciātus used as an abstract noun.…

Etymology from Wiktionary, CC BY-SA 3.0