Source : Webster's Revised Unabridged Dictionary (1913)

Southeaster \South`east"er\, n.
   A storm, strong wind, or gale coming from the southeast.

Southeaster \South`east"er\, adv.
   Toward the southeast.

Source : WordNet®

southeaster
     n : a strong wind from the southeast [syn: {sou'easter}]