How to Say "stiffener" in Spanish
The Spanish word for “stiffener” is “refuerzo” — B1 level. This is a very common word in everyday Spanish.

Examples
El muro necesita un refuerzo de acero para no caerse.
The wall needs a steel reinforcement so it doesn't fall down.
El oficial pidió refuerzos por radio inmediatamente.
The officer asked for backup over the radio immediately.
Necesitamos un refuerzo en el equipo de ventas para terminar el proyecto.
We need extra support in the sales team to finish the project.
Always Masculine
Even though it relates to 'la fuerza' (strength), which is feminine, 'el refuerzo' is always masculine.
People as Things
When talking about 'refuerzos' in the plural, it often refers to a group of people (like soldiers or police) acting as a single unit of help.
Refuerzo vs. Esfuerzo
Mistake: “Hice mucho refuerzo para ganar.”
Correction: Hice mucho esfuerzo para ganar.
Related Translations
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