Definition of "Hero" :

noun: the principal character in a play or movie or novel or poem

noun: a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States

noun: (Greek mythology) priestess of Aphrodite who killed herself when her lover Leander drowned while trying to swim the Hellespont to see her

noun: someone who fights for a cause

noun: (classical mythology) a being of great strength and courage celebrated for bold exploits; often the offspring of a mortal and a god

noun: a man distinguished by exceptional courage and nobility and strength

"RAF pilots were the heroes of the Battle of Britain."

noun: Greek mathematician and inventor who devised a way to determine the area of a triangle and who described various mechanical devices (first century)