noun which may take the genitive case particle 'no', noun
unreached; unattained; unprecedented
Formal, often used in set phrases like 未到の領域 (unreached territory) or 前人未到 (unprecedented by predecessors). Describes a state or achievement that has not yet been reached.
彼は前人未到の記録を打ち立てた。
He set an unprecedented record.
その研究は未到の領域に踏み込んでいる。
The research is stepping into uncharted territory.
Compound of 未 (not yet) and 到 (arrive, reach). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for expressing negation of attainment.