Plain English Meaning
A clip-on device, usually worn on a fingertip, that shows how much oxygen is in your blood and how fast your heart is beating.
Full Definition
A small electronic device that measures the percentage of oxygen saturation in the blood (SpO2) and the pulse rate by shining light through a fingertip or earlobe.
Context Anchor
Seen in high-altitude flying and oxygen-system discussions, especially when checking whether supplemental oxygen is keeping the pilot adequately supplied with oxygen.
Derivation
From 'pulse' (the heartbeat felt in the arteries) and 'oximeter' (a device that measures oxygen). 'Oxi-' comes from oxygen, and '-meter' from the Greek 'metron' meaning 'measure.' So literally: a device that measures oxygen and pulse.
Why Pilots Care
Early detection of falling oxygen saturation prevents hypoxia before noticeable symptoms impair or .