Plain English Meaning

Feeling great for no real reason. In hypoxia, the brain isn't getting enough oxygen, but instead of feeling unwell the pilot feels happy, relaxed, or overly confident — which is dangerous because nothing seems wrong.

Full Definition

A false sense of well-being, confidence, or contentment that can occur as an early symptom of hypoxia, where the pilot feels unusually good or capable while their performance and judgment are actually deteriorating.

Context Anchor

Seen in aeromedical discussions of hypoxia symptoms, especially during flight at higher altitudes or in any situation where oxygen supply is reduced.

Derivation

From the Greek 'euphoria,' meaning 'power of bearing easily' — from 'eu' (well) and 'pherein' (to bear or carry). The sense is of feeling everything is going easily and well. In aviation this is exactly the trap: the pilot feels things are easy at the very they are not.