[kroo-seyd] 
noun, verb, -sad⋅ed, -sad⋅ing.| 1. | (often initial capital letter ) any of the military expeditions undertaken by the Christians of Europe in the 11th, 12th, and 13th centuries for the recovery of the Holy Land from the Muslims. |
| 2. | any war carried on under papal sanction. |
| 3. | any vigorous, aggressive movement for the defense or advancement of an idea, cause, etc.: a crusade against child abuse. |
| 4. | to go on or engage in a crusade. |
| cru·sade (krōō-sād') n.
To engage in a crusade. [French croisade and Spanish cruzada, both ultimately from Latin crux, cruc-, cross.] cru·sad'er n. |
A series of wars fought from the late eleventh through the thirteenth centuries, in which European kings and warriors set out to gain control of the lands in which Jesus lived, known as the Holy Land. At that time, these areas were held by Muslims. The Crusaders conquered Jerusalem in 1099 but failed to secure the Holy Land, and they were driven out by the late thirteenth century. Nevertheless, the Crusades had several lasting results, including the exposure of Europeans to the goods, technology, and customs of Asia.
Note: The Crusades left a legacy of bitterness against Europeans and Christians among Muslims.