crusade

Definitions:

To join in a crusade.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (verb, noun) (v. & n.) (verb, noun)
A military expedition under the banner of the cross engaged in by one of the Christian powers to recover the Holy Land; vigorous concerted action for the defense of some cause, or the advancement of some idea; as, the crusade against slavery.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
Expedition to recover the Holy Land; religious or fanatical expedition.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)
A romantic undertaking.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
A military expedition under the banner of the cross to recover the Holy Land from the Turks: any daring or romantic undertaking.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)
Crusader.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
To engage in a crusade.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (verb) (v. i.) (verb intransitive)
One of those military expeditions undertaken during the middle ages under the banner of the cross for the recovery of the Holy Land from the power of the Saracens; any hostile joint enterprise conducted in a similar enthusiastic or fanatical spirit.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)

Usage examples:

A Crusade publicly proclaimed by the Pope.
- Letters of Catherine Benincasa by Catherine Benincasa
Among many high concerns, here entertained, was the project of a crusade against the Barbary States, in order to accomplish the complete abolition of Christian slavery there practised.
- White Slavery in the Barbary States by Charles Sumner
They talked rather of the chances for worldly fame and gain which the crusade presented, and aroused a desire in many of their countrymen to win both heavenly and earthly glory by an expedition to the Holy Land.
- The Story of Norway by Hjalmar H. Boyesen