Since I don't give a fuck about heroes and think they're not the people you should admire, I'll just paste the definition from wiktionnary:
1. A real or mythical person of great bravery who carries out extraordinary deeds.
2. A role model.
3. The main protagonist in a work of fiction.
4. A champion.
5. An unwilling sufferer of an act of terrorism, terminal disease, or other tragedy.
6. A large sandwich made from meats and cheeses; a hero sandwich
7. Someone who possesses supernatural powers (in fiction) such as Spiderman.