noun
chivalrous spirit; chivalrous man; knight in shining armor
Refers to a man who acts with chivalry, defending the weak and upholding justice, often in a somewhat old-fashioned or romanticized way. Can also denote the spirit itself.
彼は困っている人を見ると放っておけない、まさに男伊達だ。
He can't ignore people in trouble; he's a true knight in shining armor.
男伊達を気取って
Acting the chivalrous man, he helped her.
noun
ruffian pretending to be chivalrous
A less common, somewhat dated usage for a rough person who puts on a show of chivalry, often with an underlying selfish or violent nature.
あの男は男伊達を装っているが、実はただの乱暴者だ。
That man pretends to be chivalrous, but he's really just a ruffian.
任侠 refers more to the yakuza code of chivalry and honor, while 男伊達 is a broader, more romanticized term for a chivalrous man or spirit, not necessarily tied to organized crime.
騎士道 is the Western concept of knighthood and chivalry, whereas 男伊達 is a native Japanese term for a chivalrous man or spirit, often with a more down-to-earth, sometimes theatrical nuance.
Compound of 男 (man) and 伊達 (dandyism, showiness). Originally referred to a man who dresses stylishly and acts with bravado, later acquiring the meaning of a chivalrous man who defends the weak. The exact historical derivation is uncertain.