What is the true defination of a hero?
Someone who transcends her own limitations, risks everything, and forgets herself, while helping to relieve the suffering of another person.
But in this definition of a Hero, only another person can decide whether or not to call you a "hero." It's not for the hero to call herself a "hero."
In the act of heroism, there is no ego. Only acting automatically for the highest good, in accordance with your true nature. The hero isn't actually "doing" anything, because the "doer" isn't there at the time.
So "hero" is just a label that other people give to someone who demonstrates selfless action for the benefit of another.
We can all perform small acts of heroism, that nobody even notices or appreciates, every day. And sometimes when we have an opportunity to perform a big act of heroism, the whole world takes notice and calls you a Hero. The world is full of heroes.