Webster's Revised Unabridged Dictionary · 1913

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(Physiology Chemistry) a hormone secreted by the adrenal medulla that acts as a powerful stimulant in response to fear or stress; it stimulates autonomic nerve action. It can be obtained as a crystalline substance, C9H13NO3. It is used in medicine as a vasoconstrictor (hemostatic) and cardiac stimulant, also to reduce allergic reactions and to stimulate the heart in cases of cardiac arrest. — MI11