Refers to a person who opens up new land, a new field, or a new frontier. Can be used literally for frontier settlers or figuratively for trailblazers in any domain.
He was a pioneer of the American West.
彼女はこの分野の開拓者として知られている。
She is known as a pioneer in this field.
He is a pioneer of the internet industry.
She became a pioneer in that field.