Source : Webster's Revised Unabridged Dictionary (1913)

Slogan \Slo"gan\, n. [Gael. sluagh-ghairm, i.e., an army cry;
   sluagh army + gairm a call, calling.]
   The war cry, or gathering word, of a Highland clan in
   Scotland; hence, any rallying cry. --Sir W. Scott.

Source : WordNet®

slogan
     n : a favorite saying of a sect or political group [syn: {motto},
          {catchword}, {shibboleth}]