A stupid person; someone lacking intelligence or common sense (insulting).
From 'dull' + 'head' (the seat of intelligence). This compound noun directly insults someone's mental capacity by suggesting their head or mind is dull, similar to blockhead.
Dullhead is a direct insult that suggests someone's entire skull is full of dullness—it's more colorful and physical than just calling someone stupid, like their very head is the problem!
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