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uncivilized; uncivilised; primitive; savage
undeveloped (land); unexplored (territory, field, etc.)
unbloomed (flower)
未開の地を探検した。
We explored an uncharted land.
冒険家は未開の地を探検しに出発しました。
The adventurer explores undeveloped land.
未開部族と文明人が初めて接触した様子が映像に収められた。
The first contact between the tribe and modern people was captured on film.