Definition of "potrero"

Her driver was new to the country; he mightn't be prepared for the leaping of the yellow water down dry arroyos, swift as the pouncings of a cat, or the snake-like slidings of tons of loosened rock and clay from the steep potreros […]

1931, Mary Hunter Austin, Starry Adventure, page 274

They went to work on the green colts daybreak Sunday morning, dressing in the half dark in clothes still wet from their washing them the night before and walking out to the potrero before the stars were down, eating a cold tortilla wrapped around a scoop of cold beans and no coffee and carrying their forty foot maguey catchropes coiled over their shoulders.

1992, Cormac McCarthy, All the Pretty Horses, page 105