whats adrenaline

in my opinion an adrenaline rush is something that gives me a hightened sense of everything around my kind of like a high. Some People like jumping out planes, swimming with sharks, or racing cars and bikes which can be fun cause its dangerous but thats all it is . i believe my biggest adreanline rush is fighting because its either you or the other man thats going down thats how i see it. and im not kind to losing but yeah thats adrenaline.