adrenaline

This term functions both as a biological designation for a specific hormone and as a cultural shorthand for high-intensity excitement. In a medical sense, it describes the physiological trigger for the fight-or-flight response, characterized by rapid heart rate and heightened alertness. In common parlance, it is almost always paired with the word rush to describe the psychological thrill of danger or competition. It carries a positive connotation of vitality and energy, though it can also imply a state of nervous agitation or stress.