The Collaborative International Dictionary of English v.0.48:

Northeastern \North`east"ern\, a.
   Of or pertaining to the northeast; northeasterly.
   [1913 Webster] Northeastward

WordNet (r) 3.0 (2006):

northeastern
    adj 1: situated in or oriented toward the northeast; "the
           northeasterly part of the island" [syn: northeastern,
           northeasterly, northeast]
    2: of a region of the United States generally including the New
       England states; New York; and sometimes New Jersey and
       Pennsylvania