noun
undeveloped land; backward region; savage land
Refers to land that is not yet developed or civilized, often with a connotation of being primitive or barbaric. Can be used historically or in modern contexts for remote, undeveloped areas.
その探検家はアマゾンの未開地を調査した。
The explorer surveyed the undeveloped areas of the Amazon.
かつてこの地域は未開地と呼ばれていた。
This region was once called a savage land.
未開発 means 'undeveloped' in a more neutral, economic sense, without the connotation of being barbaric or primitive.
Compound of 未 (mi, 'not yet') + 開 (kai, 'open' or 'civilized') + 地 (chi, 'land'). Literally 'land not yet opened/civilized'.