Entering a situation without being fully prepared.
Origin: Muskets and revolvers have a lowered, half-cocked, and full-cock position for the hammer. During loading, the weapon is brought to a half-cock. The weapon must then be brought to a full-cock to be used. Forgetting to cock the weapon leads to it being unprepared for combat.
The boxer did'nt do any research on his opponent, and went off half-cocked to fight somebody twice his size.
When your penis is half hard and half soft. Morning wood is technically a type of half cocked because it isn’t quite a full boner. When ones dick is half cocked the split stream is very much common. And, being half cocked always seems to sneak up on you when you don’t suspect it. Like at school or even at church.