Plain English Meaning
A small gland sitting on top of each kidney that pumps out stress hormones, making the heart race and the body go into alert mode when a person feels threatened or under pressure.
Full Definition
A small endocrine gland located on top of each kidney that releases hormones — most notably adrenaline (epinephrine) — in response to stress, triggering the body's fight-or-flight response by raising heart rate, blood pressure, and alertness.
Context Anchor
Seen in aviation human factors discussions about normal physical reactions to stress during training, emergencies, or high-workload flying.
Derivation
From Latin 'ad-' meaning 'near' or 'on top of' and 'renes' meaning 'kidneys.' Literally 'the gland on the kidney,' which is exactly where it sits. Knowing this anchors the location and why adrenaline is named after it.