just person; man of justice; righteous person
Refers to a person, typically a man, who is strongly committed to justice and moral uprightness. Often carries a slightly old-fashioned or idealistic tone.
彼は正義漢で、不正を見逃せない性格だ。
He is a man of justice and cannot overlook wrongdoing.
That politician is known as a righteous person.
Compound of 正義 (justice) and 漢 (man, often with a connotation of a sturdy or principled man). The exact historical derivation is uncertain, but the word likely emerged in the modern period to describe an upright man.