The position of a gun's hammer when pulled back halfway, where the gun is partially cocked but not yet ready to fire; also used metaphorically.
Compound of 'half' and 'cock' (the hammer of a gun), describing a firearm's mechanical position achieved by pulling the hammer partway back.
The phrase 'go off at half-cock' became an idiom meaning 'fail prematurely or through being unprepared'—it comes from guns accidentally firing when the hammer wasn't fully locked in place.
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