Source : Webster's Revised Unabridged Dictionary (1913)

Crusade \Cru*sade"\ (kr?-s?d"), n. [F. croisade, fr. Pr.
   crozada, or Sp cruzada, or It. crociata, from a verb
   signifying to take the cross, mark one's self with a cross,
   fr. L. crux cross; or possibly taken into English directly
   fr. Pr. Cf. {Croisade}, {Crosado}, and see {Cross}.]
   1. Any one of the military expeditions undertaken by
      Christian powers, in the 11th, 12th, and 13th centuries,
      for the recovery of the Holy Land from the Mohammedans.

   2. Any enterprise undertaken with zeal and enthusiasm; as, a
      crusade against intemperance.

   3. A Portuguese coin. See {Crusado}.

Crusade \Cru*sade"\, v. i. [imp. & p. p. {Crusaded}; p. pr. &
   vb. n. {Crusading}.]
   To engage in a crusade; to attack in a zealous or hot-headed
   manner. ``Cease crusading against sense.'' --M. Green.

Source : WordNet®

crusade
     v 1: 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; "The liberal party pushed
          for reforms"; "She is crusading for women's rights";
          "The Dean is pushing for his favorite candidate" [syn: {fight},
           {press}, {campaign}, {push}, {agitate}]
     2: go on a crusade; fight a holy war

crusade
     n 1: a series of actions advancing a principle or tending toward
          a particular end; "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" [syn: {campaign},
           {cause}, {drive}, {movement}, {effort}]
     2: any of the more or less continuous military expeditions in
        the 11-13th centuries when Christian powers of Europe
        tried to recapture the Holy Land from the Muslims