free person; free spirit
Refers to someone who lives according to their own values, unbound by social conventions or obligations. Often carries a positive, slightly unconventional nuance.
He quit his job and is traveling the world as a free spirit.
She's a free person, so working fixed hours doesn't suit her.
自由人 is a free person with full personal liberty, the direct opposite of 奴隷, who has no freedom.
Compound of 自由 (freedom) and 人 (person). The exact historical derivation is uncertain, but the term is a straightforward modern coinage.