What is the meaning of 東北?

northeast

(~地區) Northeast China (a region of China; consisting of Liaoning, Jilin and Heilongjiang, and sometimes the northeast part of Inner Mongolia)

(大行政區, ) Northeast China (a former greater administrative region of China from 1949 to 1954, consisting of Liaodong, Liaoxi, Jilin, Heilongjiang, Songjiang, Rehe and Suiyuan, Shenyang, Lüda, Fushun, Anshan and Benxi)

Manchuria

(~地方) Tōhoku (a region of Japan)

northeast

Tōhoku (a traditional region of Japan, specifically the northernmost six prefectures in Honshu (clockwise from the northermost): Aomori, Iwate, Miyagi, Fukushima, Yamagata and Akita)

hanja form of 동북 (northeast)

chữ Hán form of đông bắc (northeast).

Source: wiktionary.org