a pebble
Tom tiró un guijarro a la ventana del dormitorio de Mary.
Tom threw a pebble at Mary's bedroom window.
Hallaste un guijarro en el tanque.
You found a pebble in the tank.
— Ace Ventura: Detective de Mascotas (1994)
Yanni encontró un guijarro bajo su cama.
Yanni found a pebble under his bed.