atesar

An obscure, now largely obsolete verb functioning as a rare synonym or older form of atiesar (to stiffen) — it barely appears outside historical dictionaries and specialized regional use, and modern speakers reach for atiesar or endurecer instead.

• El frío atesó las cuerdas del tendedero. — The cold stiffened the clothesline ropes.
• La ropa mojada se atesó al congelarse. — The wet clothes stiffened as they froze.
• El cuero viejo se atesó con los años. — The old leather stiffened over the years.

Using atesar in everyday speech expecting to be understood — it's essentially obsolete; atiesar is the form virtually all speakers actually use for 'to stiffen.'

Often confused with atiesar.