Final answer:
Sudden, intense fear is known as Panic, which triggers the body's fight-or-flight response due to hormone release by the adrenal glands.
Step-by-step explanation:
Sudden, intense fear is best described as Panic. The physiological responses to fear, such as a racing heart, rapid breathing, and clammy hands, are due to the release of hormones by the adrenal glands. These responses are part of the body's fight-or-flight mechanism, preparing an individual to either defend themselves or escape from danger. This reaction happens not only in extreme situations but can also be triggered by perceived threats or overwhelming stress, as indicated in the provided references, ranging from literary characters experiencing overwhelming dread to individuals experiencing generalized anxiety disorders with potential impact on cardiovascular health.