las costas

back (of the body)

ˈk o s t a s → costa
cost coast + as plural
noun · feminine plural Rare #46,237
back (of the body) Usually used in the expression "a espaldas/a costas de" meaning "behind someone’s back".
SP: Lo hicieron a sus costas.
EN: They did it behind his back.
Declension of costa
costacostas

La Marina defiende nuestras costas.

The Navy defends our coasts.

Él quería triunfar aún a costas de su salud.

He wanted to succeed even at the cost of his health.

Él la salvó a costas de su vida propia.

He saved her at the cost of his own life.

Mi gente se va de estas costas.

My people are leaving these shores.

— El señor de los anillos: La comunidad del anillo (2001)