A word that has recently been overused in the American English vocabulary. It has been automatically bestowed upon people in the law enforcement, armed forces, or fire/rescue services, as well as presidents. I.e. police officers, soldiers, and fire fighters and paramedics. A hero, however, does not require wearing a uniform or be involved in such professions listed above.
The basic definition of a hero is one who does not recognize such declarations bestowed upon them by others and accomplishes an act or acts which are deemed extraordinary and exceeds the call of duty. This act or acts usually involves the intention or consequence of saving another person(s) life or rescuing another from impending harm.
"Did you hear what Tony did? He jumped into a pool of alligators and rescued a little girl. He is such a hero! And to think I never noticed him in the accounting department!", fawns the blonde bombshell to her voluptuous and stacked brunette friend.