A person who supports feminism; used for both men and women. The primary modern meaning.
She is a passionate feminist and strongly advocates for gender equality.
man who is attentive to women; gentleman
A somewhat dated or colloquial use, describing a man who treats women with special kindness or chivalry, sometimes with a nuance of indulgence. Not the primary meaning.
He always opens doors for women; he's a bit of a gentleman.
He calls himself a feminist, but his actions are often contradictory.
Many young people have started calling themselves feminists.