Tomboy refers to a female whose behavior is free from the restriction of unwritten societal gender rules. She doesn't think she is being boyish or girlish, she is being herself. It is hopefully considered an old-fashioned term. I've always been called a tomboy and I hear it when I do something that requires physical strength or when I'm playing and don't mind getting dirty or injured if that goes with the game. I am heterosexual by instinct and choice. Tomboys are usually willing to fight if necessary & tend to be fearless though not stupid in that respect. They are intolerant of bullies and tend to step in to balance uneven situations. Warrior-like in an honorable way.
Joe: "Brigit jumped right in the middle of that fight to help Ben! She's 50 and such a sexy woman, I wasn't expecting that."
Mike: "She's what you older guys call a tomboy. Really, she's being herself and happens to be a person who's willing to fight."