Definition of: crusade

(kr·sād′) noun
1. Any of the military expeditions undertaken by European Christians from the 11th through the 13th century to recover the Holy Land from the Moslems.
2. Any expedition under papal sanction against heathens or heretics.
3. Any vigorous concerted movement or cause, especially against public evil.
—v.i. ·sad·ed, ·sad·ing To go on or engage in a crusade. [<Sp. cruzada <Med. L cruciata a crossing <cruciare mark with a cross <L crux a cross; infl. in form by related F croisade]
—cru·sad′er noun