U

burnout

noun

a fire that is totally destructive of something.
Also burn-out. fatigue, frustration, or apathy resulting from prolonged stress, overwork, or intense activity.
Rocketry.
1. the termination of effective combustion in a rocket engine, due to exhaustion of propellant.
2. the end of the powered portion of a rocket’s flight.
Electricity. the breakdown of a lamp, motor, or other electrical device due to the heat created by the current flowing through it.

also burn-out, “drug user,” by 1972, slang, from the verbal phrase, from burn (v.) + out (adv.). Meaning “mental exhaustion from continuous effort” is from 1975.