na-adjective, noun which may take the genitive case particle 'no', noun
strong-minded; spirited; mannish
Describes a woman or girl who is more capable, assertive, or physically strong than typical men; can be positive or mildly critical depending on context.
彼女は男勝りの性格で、誰にも負けない。
She has a strong-minded personality and won't lose to anyone.
姉は男勝りで、力仕事も平気だ。
My older sister is mannish and doesn't mind heavy lifting.