How to Say "thick-headed" in Spanish
The Spanish word for “thick-headed” is “melón” — B1 level.

Examples
¡No seas melón! La llave gira hacia el otro lado.
Don't be a dummy! The key turns the other way.
Mi hermano es un melón y siempre olvida su cartera.
My brother is a bit of a bonehead and always forgets his wallet.
Le expliqué la tarea tres veces, pero es un poco melón.
I explained the homework three times, but he's a bit slow.
Using 'Ser'
Use the verb 'ser' (to be) with this meaning because you are describing a characteristic of the person, even if it's temporary: 'Eres un melón'.
Noun as Adjective
Even though 'melón' is a noun (a thing), in this context it acts like a description for a person. It usually stays masculine if referring to a guy, but you might hear 'melona' for a girl in some regions, though 'melón' is more common for both.
Tone Warning
Mistake: “Using this word with a stranger.”
Correction: This is informal. Only use it with people you know well, or it might sound rude instead of funny.
Related Translations
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