東北 does mean “northeast” and is a synonym for 北東, though it’s also an abbreviation of 東北地方. One of the hidden synonyms for it on WK is “northeast,” which is why you spelling it as two words was counted as a little bit off—it falls within typo allowance of that accepted answer.
The first definition is “the direction between east and north,” and then it’s additionally defined as 北東 and うしとら, which are both words meaning “northeast.” The second definition is its use as an abbreviation for “Touhoku Region.”