Source : Webster's Revised Unabridged Dictionary (1913)

Southeastern \South`east"ern\, a.
   Of or pertaining to the southeast; southeasterly.

Source : WordNet®

southeastern
     adj 1: situated in or oriented toward the southeast [syn: {southeast},
             {southeasterly}]
     2: of a region of the United States generally including
        Alabama; Georgia; Florida; Tennessee; South Carolina;
        North Carolina