The Collaborative International Dictionary of English v.0.48:

Dardanelles \Dardanelles\ n.
   1. the strait between the Aegean and the Sea of Marmara that
      separates European from Asian Turkey.

   Syn: Hellespont.
        [WordNet 1.5]

   2. the unsuccessful campaign in World War I (1915) by the
      English and French to open a passage for aid to Russia;
      defeated by the Turks.

   Syn: Dardanelles campaign.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Dardanelles
    n 1: the strait between the Aegean and the Sea of Marmara that
         separates European Turkey from Asian Turkey [syn:
         Dardanelles, Canakkale Bogazi, Hellespont]
    2: the unsuccessful campaign in World War I (1915) by the
       English and French to open a passage for aid to Russia;
       defeated by the Turks [syn: Dardanelles, Dardanelles
       campaign]