WordNet (r) 3.0 (2006):

rallying cry
    n 1: a slogan used to rally support for a cause; "a cry to
         arms"; "our watchword will be `democracy'" [syn: war cry,
         rallying cry, battle cry, cry, watchword]
    2: a yell intended to rally a group of soldiers in battle [syn:
       war cry, war whoop, rallying cry, battle cry]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "rallying cry":
   Angelus, Angelus bell, alarm, alarum, bark, battle cry, bawl,
   bellow, birdcall, bugle call, call, call to arms, call-up,
   catchword, caterwaul, cheer, clarion, clarion call, conscription,
   cry, exhortation, go for broke, gung ho, halloo, holler, hollo,
   hoot, howl, hurrah, last post, levy, mobilization, moose call,
   motto, muster, rally, rebel yell, recruitment, reveille, roar,
   scream, screech, shout, shriek, slogan, squall, squeal, summons,
   taps, trumpet call, war cry, war whoop, watchword, whistle, whoop,
   yammer, yap, yawl, yawp, yell, yelp, yo-ho, yowl