Arrogantly or excessively confident; certain in a way that is annoying or shows overconfidence, even when you're probably wrong.
From 'cock' (rooster, symbolizing boldness and aggression) + 'sure' (certain). The word emerged around the 1600s to describe someone with a rooster's unwarranted confidence and swagger.
The word perfectly captures rooster behavior—they strut around looking 100% confident even in ridiculous situations, and cocksure people do exactly the same thing, strutting through life convinced they're right when they probably aren't.
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